In February 2000, Golden Software announced the release of Didger 2.0, a package for digitizing a variety of cartographic and graphic information (Fig. 1). This product significantly expands the capabilities implemented in the first version (a complete overview of Golden Software products is given in ComputerPress 11'99 and 2'2000 on CD).
It should also be noted that already in March of this year, Golden Software released an updated version of this program 2.01, which eliminated the error associated with the inability to activate the digitization mode in version 2.0 after calibrating the tablet. The situation is quite common, but something else is curious - the company itself sent out a CD with the updated program to all registered users, confirming in practice that ensuring high standards of user support is not a simple declaration, but a very real matter.
A simple listing of the package's innovations includes more than fifty points, so we will note only the most significant, in our opinion.
Screen digitization of raster images
The program expands the capabilities of traditional operations for digitizing maps using a digitizer. At the same time, Didger 2 provides direct support for any similar devices that comply with the WinTab32 standard.
One of the most significant improvements in Didger 2 is its ability to digitize raster and vector images directly on the screen using a keyboard or mouse (Figure 2). This feature is essential for a wide range of tasks.
The package allows you to import graphic files in 32 different formats and includes a whole set of tools for image processing and coordinate conversion. Scanning of raster images is performed by the built-in support of TWAIN-standard hardware or by external programs that can be integrated into the Didger environment. Digitization results can be exported either with or without the original image used for digitization. You can use 14 different file formats to export data, including GeoTiFF.
Georeferencing and projection conversion
Didger 2 is the first Golden Software product to support over 20 map projections: UTM, State Plane 1927, State Plane 1983, Albers Equal Area Conic, Eckert IV and VI, Equidistant Cylindrical, Gauss-Kruger/Gauss-Conformal, Lambert Azmuthal Equal Area , Lambert Conformal Conic, Mercator, Miller Cylindrical, Molleweide, Orthographic, Polyconic, Robinson, Robinson-Sterling, Sinusoidal, Stereographic, Transverse Mercator and Unprojected Lat./Long. (The MapViewer program, which previously implemented functions for converting coordinate systems, includes only three types of projections.) At the same time, users were able to convert maps from one projection to another, as well as import, create and export georeferenced files to any of the listed projections ( Fig. 3). It is significant that you can now set projection parameters when importing data and vector files.
Coordinate transformation
The process of converting data and coordinate systems has been significantly simplified. Thus, transforming image coordinates using simple mathematical operations or new georeferencing methods, including the Affine method and first, second and third order polynomials, is used to recalibrate images and data (Fig. 4). The coordinate conversion function is designed to modify the current vector database, including conversion from one coordinate system to another. (In contrast to the methods for converting geographic projections described above, in this case we primarily deal with the problem of re-stretching images in order to minimize distortion by photocopying maps, stitching sheets, etc.)
In addition, Didger 2 now has the ability to specify source data taking into account datum standards (various methods for determining cartographic parameters) and perform information transformations using the following methods: Molodensky, Bursa-Wolfe, DMA Multiple Regression Equations, as well as user-specified ones.
In the process of transforming spatial data when moving from local to geographic coordinates and vice versa, an error assessment is made for the selected project. You can also set the operating mode within specified standards based on statistical calibration methods.
Import/export capabilities
Didger 2 includes many new advanced import/export filters that make it easier to transfer data and images to and from other applications:
- Spatially Referenced images can be imported/exported using the following formats: GeoTIFF, TFW and RSF. This provides full support for all GeoTIFF parameters;
- new vector import formats (Vector Import): GSB, BNA, DLG, LGO, LGS, DXF, PLT, BLN, CLP, WMF, SHP, MIF, DDF and E00;
- new raster image import formats (Raster Import): TIF, BMP, TGA, PCX, GIF, WPG, DCX, EPS, JPG and PNG;
- new formats for importing point data (Data Import): DAT, CSV and TXT;
- new export formats: EMF, SHP, GIF, CGM, MIF, CLP, TIF, TGA, PCX, WPG, PNG, JPG, PCT and DCX.
Creating multi-layer maps
Didger 2 now supports many features that were previously implemented in geographic information systems. For example, here you can not only digitize maps, but also supplement images with your own custom elements (text labels, lines, raster insets, etc.). In particular, it became possible to construct curved lines on a plane using various methods. The maps themselves are now created as a multi-layered system using a wide range of drawing, filtering and data transformation tools. At the same time, the user has at his disposal a convenient set of tools for managing map objects, including data processing functions: search, rejection, filtering, transformation, etc. (Fig. 5).
Data Attribute View Window
The appearance in Didger 2 of the Data Attribute View window, dynamically linked to the Plot window, was very useful. Select an object in one of these windows, and you will see that the same object will be simultaneously selected in the other window (Fig. 6). In addition, users have the opportunity to flexibly control the placement of the Data Attribute View window on the screen, which now acts as an object manager available at any time. Object information presented in this window includes the following: type, primary and secondary identifiers, primary and secondary groups, layer name, number of points, perimeter length, area and direction of the closed area figure. All this information can be printed.
Adjusting line connections
When digitizing lines, quite often the problem of inconsistency when connecting lines arises. In Didger 2 this task is solved very simply. If any line does not reach the adjacent line, and you need them to touch, use the Snap Undershoot Polyline command - and then the short line will be extended (Fig. 7a). If you have digitized a line so that it extends beyond the adjacent line, and you need to construct an exact intersection, use the Trim Overshoot Polyline command - and the protruding line will be trimmed (Fig. 7b).
Working with area shapes
To create closed area figures from several individual lines, Didger 2 has a new object - Polygon Marker. Place it in the center of the group of lines that you want to form a new area shape, and then use the Create Polygons by Locator command, which will instantly create a closed polygon.
To create complex maps by grouping selected areas, Didger 2 introduces a new Combine Island/Lakes command. Thanks to the Reverse Island/Lakes command, you can completely control the orientation of the area, transform an island into a lake, and vice versa. If necessary, you can, of course, ungroup the area and reassign IDs to all individual objects.
Didger 2 costs $329, Upgrade version costs $99 (Golden Software catalog price). Plus the cost of shipping from the USA to Russia is $60 ($10 for each additional copy). As with all Golden Software products, Didger 2 comes with a 30-day warranty, during which you can return the product for your money back, and lifetime technical support.
More information about Didger 2, including its demo version, can be found on the Web page at: www.goldensoftware.com. Extended information about Golden Software products in Russian can be found at: www.visual.2000.ru/golden/.
ComputerPress 6"2000
IN Surfer provides the ability to remove values X and Y coordinates at arbitrary points of both constructed grid maps and raster images imported from outside. This process is called digitizing. Most often it is used to convert old scanned raster maps into electronic form. Importing such maps for subsequent digitization is done by creating a base map.
III.1. Creating a Base Map
The base map allows you to display information in the plot document window that cannot be represented in the form of a grid map. Most often, the host map is a raster image imported from an external graphics file. In this case, the coordinates of this map are the pixel number, counting from the lower left corner of the image. The base card can be combined with any other type of card.
To create a base map you need:
1. Create a new raft document. Save it under the name “Black Sea.srf”.
2. Run command Map/Base Map or click on the Map toolbar button. The Open dialog box will appear (Figure I.10). Select the graphic file “BlackSea.jpg”.
3. If you click on the button, then in the middle of the page shown in the plot document window, a newly created base map will appear, depicting a fragment of the map of the gravitational field over the Black Sea and adjacent territories (Fig. III.1).
Map base: gravitational field over the Black Sea and surrounding areas
4. Give the name “Gravika” to the base map.
Rice. III.2. Digitizer window after the first click on the base map to be digitized
III. 2. Digitization of the base map
Digitizing the base map allows you to convert it into electronic form. To do this you will need:
1. Select the Gravika map with a single click.
2. Run command Map/Digitize . The mouse pointer will change to a thin cross. As you move the pointer over the map, the status bar will show the map's current X and Y coordinates.
3. Left-click on the map. The digitizer window will appear (Fig. III.2). A line with coordinate values will be automatically added in this window X and Y . In addition, a small (unfortunately temporary) red cross will appear on the map in the place where the click was made.
4. Thus, it is necessary to track the entire digitized isoline.
5. Save the results of digitizing each isoline separately. In the digitizer window, run the command File/Save As . The Save As dialog box will appear (Figure I.8). In the Save as Type drop-down list, select Data Files (*.DAT). Enter the file name in accordance with the value (taking into account the sign) of the isoline being digitized.
6. Close the digitizer window and start digitizing the next isoline.
7. To end the digitization process, press the key Esc.
Task 17. Digitizing a raster image
(Labour intensity 10)
1) Create a new raft document “Black Sea”. Create a base map from the graphic file “BlackSea.jpg”. Digitize all isolines of the gravity field.
2) After passing the next contour, construct a point map based on the newly created file with the digitization results. In the object manager, give a name to each point map in accordance with the value of the digitized isoline. Include dot maps in overlay with base map.
3) Assemble all digitization results in a single file in worksheet mode, adding a third column - the gravity field value for each isoline. Save in the file “Assembly.dat”.
4) Create a grid file “Assembly.grd” based on the data in the file “Assembly.dat”.
5) Construct a contour map based on the grid file “Assembly.grd”. Set the outline color of all isolines to white.
Digitization is the process of converting features shown on a paper map into a digital format. To digitize a map, you can use a graphics tablet (digitizer) connected to a computer, with which you will enter objects. The x,y coordinates of these objects are automatically recorded and stored as spatial data.
Digitization using a digitizer is an auxiliary means of creating and editing spatial data. You can convert almost any paper map features into digital features. You can use the digitizer in conjunction with ArcMap tools to create new features or edit existing digital map features.
You can digitize features and add layers to an existing map, or create a new set of layers for new areas for which data has not yet been created. You can also use a digitizer to update an existing layer of your digital map.
This section describes the process of preparing a map for digitization.
Step 1: Setting up the digitizer and installing the device driver
To use a graphics tablet with the ArcMap application, a WinTab compatible graphics tablet driver must be installed. To make sure that a WinTab compatible driver is available for your tablet, refer to your device documentation or contact the manufacturer.
If you installed ArcGIS before installing a graphics tablet, the Digitizer tab may not appear in the Editing Options dialog box. To add a bookmark, you must register the digitizer.dll file using the ArcGIS ESRIRegAsm.exe utility. To complete these steps, you will need administrator rights.
Clue:
If you have installed the ArcGIS ArcObjects Software Development Kit, you can search for the digitizer.dll file, right-click it, and select the command to register the device.
- Close all ArcGIS applications.
- Launch a DOS command prompt, which is usually accessed from the Start menu, Programs (or All Programs), Standard (Accessories).
- In the window, type cd followed by a space, then enter the path to the folder containing the ESRIRegAsm.exe utility: C:\Program Files (x86)\Common Files\ArcGIS\bin. This will change the active directory of the Command Prompt to the folder containing the installed ESRIRegAsm.exe utility.
- Press the Enter key.
- Type ESRIRegAsm.exe, followed by a space, open quotes, enter the full path to your ArcGIS installation directory with the file name and DLL extension, and close the quotes. The default path is "C:\Program Files (x86)\ArcGIS\Desktop10.2\bin\digitizer.dll". If you installed ArcGIS in a different directory, change the path.
- Press the Enter key.
- If registration was successful, close the window Command line. The Editing Options dialog box in ArcMap now displays a Digitizer tab after a reboot.
If ArcGIS is installed in the default location on a 64-bit Windows 7 machine, the Command line should look like this. The text you need to enter is highlighted in bold.
Microsoft Windows Copyright (c) 2009 Microsoft Corporation. All rights reserved. C:\Users\username> cd C:\Program Files (x86)\Common Files\ArcGIS\bin C:\Program Files (x86)\Common Files\ArcGIS\bin> ESRIRegAsm.exe "C:\Program Files(x86)\ArcGIS\Desktop10.2.1\bin\digitizer.dll"
Note:
This example is for Windows 7, so the paths shown in the window Command Prompt may differ if other operating systems are used. The text that needs to be entered will not change. On 32-bit OSes, only Program Files should be specified on the command line, without (x86). For example, for the 32-bit version the default path is C:\Program Files\Common Files\ArcGIS\bin.
Note:
Depending on your operating system and security settings, you may need to run Command Prompt as an administrator. From the Start menu, right-click Command Prompt, select Run as administrator and enter your details in the window User Accounts (User Account Control).
Step 2: Customize the pen keys
After installing the driver, use the WinTab Manager installer to configure the pen buttons (you may want to turn on the tablet and restart your computer before using the installer). One of the buttons must be configured to perform a single left-click to digitize vertices; the other button should be responsible for double-clicking the left mouse button to complete the digitization of linear or polygonal objects. You may also need to configure a third right-click button to access context menus.
Using various development languages, you can configure additional buttons to launch specific ArcMap commands.
Step 3: Assessing the quality of cartographic materials
The map you want to use for digitization must be reliable in terms of quality, free from mechanical damage and contain up-to-date information. Paper may wrinkle or change shape depending on weather conditions. For example, to reduce distortion associated with damage to paper originals, they can be made on a more stable material, such as Mylar.
Step 4: Setting control points on the paper original
Before you start digitizing objects from a paper map, you need to install control points, which will be used to register (reference) the map to geographic space in ArcMap. If the map has a grid or points with known coordinates, you can use them as control points. If there are no such points, then you can specify from 4 to 10 specific locations, for example, road intersections, and mark them on the map. For each location, provide a unique identifier and write down on a piece of paper the actual coordinates for the selected points.
Once you have marked at least four control points, place the map on the tablet and secure the paper original to the surface of the tablet. If the map is not aligned on the tablet surface, ArcMap will then correct the map's position during the registration (snap) process and display the offsets in an error report.
Step 5: Register (link) card
After specifying control points, you need to register (link) the map in real coordinates. This will allow you to digitize objects directly in geographic space.
During the map registration process, real coordinates for control points and coordinates of points on the tablet obtained during their digitization are used. These options are specified on the Digitizer tab in the Editing Options dialog box.
After entering actual coordinate values, ArcMap displays an error report. The error report includes two types of errors: the positions of each point and the root mean square (RMS) error for the set of points. The position error of the points is the difference in the position of the point after transformation compared to the position determined by the coordinates. The root mean square error (RMS) is the average of the displacements of each point.
ArcMap reports errors in the current map units. The root mean square (RMS) error is displayed in the current card units and in inches on the digitizer surface. If the root mean square (RMS) error is too high, you should re-register using different anchor points or remove some of the used points (so that there are at least four remaining). To maintain high digitization accuracy, the root mean square (RMS) error should not exceed 0.004 units in which the position on the tablet is measured (for example, inches) or the equivalent distance on the scale of a paper map. For less accurate data, it is enough not to exceed the root mean square error of 0.008 units.
Step 6: Setting the correct projection
If you know which coordinate system(projections) a paper map has been created, you must specify the same projection for the layer in which the digitized objects will be stored. If you are digitizing features into an existing layer, you must ensure that the layer and paper map are created in the same coordinate system.
Step 7: Enable Digitization Mode and Start Digitizing
To start digitizing objects, you must enable digitization mode.
Digitizers can operate in pen digitizing mode (absolute mode) and mouse digitizing mode (relative mode). When you are in digitizing mode (absolute mode), you can only digitize objects; You cannot select buttons, menu commands, or tools in the ArcMap interface because the pointer only works in the drawing area. However, in mouse mode (relative mode) digitizing mode, there is no correlation between the position on the tablet and the position on the screen. When digitizing, you can switch between digitizing modes and mouse modes using the Editing Options dialog box. This allows you to use the digitizer to digitize objects, as well as access the user interface (instead of the mouse). You can also use the mouse to select interface elements at any time when the digitizer is in mouse mode or digitizing mode.
You can digitize features on a paper map in two ways: in point-by-point digitization mode or in streaming digitization mode. You can switch between these modes by pressing the F8 key.
When you start digitizing, the default mode will be point-by-point digitizing. IN point digitization mode you transform features from a map by digitizing their vertices. ArcMap connects these vertices to create the shape of the features. The point digitization mode works in the same way as the substrate digitization mode on the monitor screen using construction tools; The difference between the digitizing process is the conversion of pen coordinates on the tablet instead of mouse pointer coordinates on the screen.
In streaming digitizing mode, as you move the pointer across the map, ArcMap adds vertices automatically at a certain interval. In streaming mode, it is convenient to digitize curved lines, such as rivers. Streaming or streaming digitizing is a fairly common digitizing method used with a tablet digitizer and can also be used with mouse digitizing.
To start digitizing in streaming mode, right-click on the map and select the context menu item Streaming mode when you create objects. You can also press F8 to switch to streaming mode. Clicking on the map pauses streaming. This allows you to use buttons, menus, and other user interface elements. This means that you can right-click to access a menu that allows you to place a vertex using Absolute X,Y, Incremental X,Y Coordinates, or any of the others in that menu. Click on the map again to return to streaming mode. To turn off streaming mode completely, click Streaming mode again or press F8.
Tyumenburgaz, a branch of the Gazprom drilling company, is rightfully considered the largest drilling enterprise in the industry. The main drilling targets are located over a vast area limited by 72 and 82 degrees east longitude and 63 and 69 degrees north latitude; individual deposits are located outside the specified area. Our main customers - the largest gas producing enterprises of Gazprom - use the state coordinate system in the 1942 Gauss-Kruger projection. Smaller companies prefer the 1963 coordinate system: due to the reduced level of secrecy, this provides them with significant savings. For the same reason, some enterprises work with local coordinate systems. In addition, when carrying out many types of work using satellite geodetic systems, it is more convenient to use the WGS-84 coordinate system in the UTM projection. Thus, a single standard for the preparation of surveying documentation is impossible: the surveying and geodetic service of Tyumenburgaz has to operate with cartographic and geodetic information in all of the listed coordinate systems, and in any of them the territory of the branch’s activities is located in at least two zones.
This circumstance became decisive when choosing a geographic information system (GIS): Tyumenburgaz acquired the MapInfo Professional software product and a set of electronic maps from the Federal Service of Geodesy and Cartography (FSGC). Over time, the quality of FSGC electronic maps, created on the basis of outdated sheets of topographic maps at a scale of 1:200,000, was considered insufficient: independent vectorization of large-scale topographic maps for individual areas of Tyumenburgaz’s activities was required. Since the GIS MapInfo is completely unsuitable for such purposes, we had to choose a vectorizer program...
First of all, we formulated the basic requirements for this program. Firstly, its tools must provide tracing using a color raster: topographic maps carry a large amount of information contained in color. Secondly, automatic vectorization tools are needed to speed up digitization. Thirdly, the vectorizer program must provide the ability to import data from the DGN MicroStation format and export to the DWG (DXF) AutoCAD, MIF (MID) MapInfo formats: many customer enterprises require materials to be submitted in the AutoCAD format, and provide electronic drawings in the DGN format many design organizations.
Spotlight Pro 5, developed by Consistent Software, fully met all these requirements. However, company employees warned: Spotlight Pro 5 has not yet been used by anyone to vectorize topographic maps. A year and a half has passed since then. During this time, new versions of the program have appeared, and we have accumulated some experience, which, I hope, will be of interest to Spotlight Pro users working with topographic maps...
In the beginning there was a raster...
Some practical tips before you start:
- the best results of raster-to-vector conversion are obtained on a raster with a resolution of 600−700 dpi;
- Before calibration, make sure that there is a small frame (5−6 mm) around the raster image being processed. During calibration, the image may not be compressed, but stretched - in this case, the presence of such a frame will protect the image from loss;
- If problems arise, do not rush to be loudly indignant - those around you are not to blame for anything. Report the problem to Consistent Software technical support ( [email protected]) - they will always come to your aid.
Coordinate system
So, you start vectorizing topographic maps in Spotlight Pro. How can I set a coordinate system so that the resulting data can be used in MapInfo together with existing data? What units should I use, what scale should I set, and in what order should I enter the coordinates? After experimenting a little, you come to the conclusion that the dimension of the units does not matter much: you can also use inches, the main thing is to set the scale in such a way that the resulting numerical coordinate values do not contradict the truth. We used millimeters as the user and world units and set the scale to 25 for the 1:25,000 maps.
Pay attention to the order of recording the coordinates of the Gauss-Kruger projection: y, x. Coordinate y is written indicating the zone number - this fully corresponds to the structure of the MIF file. The same entry, using the default UCS, is preferred by almost all AutoCAD users. The proposed approach was tested as follows: a map sheet with a given coordinate system was exported from Spotlight to AutoCAD, and then data obtained from the operation of satellite equipment in that area was exported to the same file. The data completely matched the image on the map.
Calibration of topographic maps
When working with topographic maps in Spotlight, the user must first solve the problem of calibrating the scanned image. Otherwise, the work of vectorizing maps is meaningless.
Green lines in Fig. 2 is the kilometer grid in the coordinate system of the map sheet. In this case, we are dealing with ordinary minor deformations, but the original image is not suitable for vectorization.
It is necessary to digitize the drawing in a rectangular coordinate system - on a map sheet it is specified by a coordinate (kilometer) grid. At the same time, by calibrating only at the intersection points of the coordinate grid (Fig. 3), we will get an excellent result inside the calibration area and completely unpredictable at the edges of the map sheet: in the area between the coordinate grid and the trapezoid frame defined by the geodetic coordinate system (latitude , longitude).
It is quite obvious that to calibrate a map sheet it is necessary to use the intersection points of the coordinate grid and the trapezoid frame. It is impossible to set the values of their real coordinates using software, so we use a fairly convenient and simple graphical method.
1st stage. In any available coordinate recalculation program, we convert the geodetic coordinates of the corners of the trapezoid frames and the points of intersection of the axial meridian of the sheet with the upper and lower sides of the trapezoid into the rectangular coordinate system used on the sheet being processed.
2nd stage. After loading the initial map raster and specifying the coordinate system, we create an auxiliary vector layer “Frame” in the Spotlight program. Using the tool, we construct the sides of the frame according to the calculated coordinates of the corners of the trapezoid frame. Using the tool, we construct the upper and lower sides of the frame: each at three points (for example, the upper left corner of the frame + the intersection of the upper side of the frame and the axial meridian of the sheet + the upper right corner of the frame). Set up the grid as a kilometer grid and turn on the mode. Then, using snapping to grid nodes, using the tools Segment by points or Polyline We build a vector kilometer grid so that the ends of the grid segments are outside the map sheet - to obtain intersections of the constructed frame and the lines of the kilometer grid.
Now we have a complete set of vector intersections to create a set of gauge pairs in the dialog Calibration. Using the tool and turning on the vector snap mode, this work is not difficult to do. Calibration pairs on a kilometer grid are easier and faster to set using the tool.
For the first time, the calibration result (Fig. 4) will simply stun you. However, this soon passes - you get used to good things quickly.
Vectorization
Let’s make a reservation right away: Tyumenburgaz is working on vectorization of maps of tundra areas, where there are practically no settlements, the vegetation is extremely poor, but areas of swamps and swamps are often found (Fig. 2).
The MapInfo data exchange format imposes strict restrictions on the types of graphic objects used: only point, line, polyline (polyline), area (closed polyline), arc, text, rectangle, rounded rectangle, ellipse are allowed. It is better to decide what types of objects we should receive before vectorization begins. The presence of objects of the “text” type in MIF files is undesirable: all text on a topographic map is either a level designation (mark) or a message about the properties of an object - in other words, its attribute. In addition, to convert MIF files from one coordinate system to another, we use the “Geographic Calculator 4.01” program, and with objects of the “text” type, this program does not work correctly, to put it mildly. An “arc” type object may well be part of a polyline describing a horizontal line or a stream, but it is extremely inconvenient for vector editing (this is the author’s personal opinion, with which you, of course, have the right to disagree). Since in our case there are almost no populated areas, there is no need to create objects of the correct shape (rectangles, rounded rectangles and ellipses) - at least in automatic mode...
The largest volume of work on vectorization of topographic maps falls on the digitization of relief and hydrography. The first place is firmly held by the horizontals. It is convenient to digitize them automatically - most objects are brown in color. But when digitizing hydrography, it turns out that too many objects are indicated in blue on the map. So for vectorizing rivers, streams, etc. It is more convenient to use tracing. But it is desirable to obtain contour lines, streams, and boundaries of lakes and rivers in the form of polylines and closed polylines, so the final set of objects for conversion looks like it is shown in Fig. 5.
Conclusion from work experience: if it is necessary to digitize hydrographic objects alone (for example, for construction design, registration of land allotments for large objects), then using color raster tracing increases productivity by 2-2.5 times. The use of automatic vectorization when completely digitizing a map sheet speeds up the work by 4-5 times. Don't take this as an advertisement, but I am truly blown away by the capabilities of Spotlight Pro! However, let's return to the digitization process.
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Having performed the binarization of shades of brown, we obtain an embedded raster, upon inspection of which you will notice that it requires some editing. In areas with a high density of contour lines, raster lines merge (Fig. 6), and the program is unlikely to be able to sort out this mess on its own.
The tool helps to cope with the situation. A few mouse movements and the embedded raster takes on a meaningful appearance (Fig. 7).
In situations like the one shown in Fig. 8, tool used [Draw points and lines on the raster].
Since after vectorization it will take time to edit the vector line, it is easier to bring the raster to the form shown in Fig. 9. After editing the raster, it will be enough to fill the holes, and such objects will be recognized as one continuous polyline.
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So, the entire process of digitizing a map sheet comes down to the following procedures:
- binarization of relief (shades of brown);
- raster to vector conversion;
- editing the resulting vectors (layering, setting levels and attributes, merging disparate polylines, etc.);
- tracing of hydrographic objects;
- digitizing the remaining objects manually (for conservative AutoCAD users, I recommend doing this part of the work in your favorite program: click Save as… and select DWG format).
Export
Exporting the obtained data from Spotlight Pro to AutoCAD is not difficult, but we should talk in more detail about exporting to MapInfo. Based on the export results, Spotlight creates two files with the same name and MIF and MID extensions. A MIF file is a database that contains information about the types of vector objects and the coordinates of their nodes (graphical information). MID file is a database of tabular data characterizing the corresponding graphic object (layer name, attribute, level, line type and color, etc.). Having a MID file is not required, but the information it contains will be useful for further work in MapInfo.
The header of the MIF file contains the “Plan-Scheme” (“NonEarth”) coordinate system and indicates the units of measurement that we chose when creating the coordinate system (Fig. 10).
Import into MapInfo will work correctly if you correct the CoordSys sentence to specify the required projection and units. As for the example shown in Fig. 10, object coordinates were obtained for the 4th zone of the Gauss-Kruger projection (axial meridian - 21 degrees, initial latitude - 0 degrees, scale factor - 1, displacement of the axial meridian along the axis y— 4,500,000 m) in meters.
The corrected MIF file header is shown in Fig. eleven.
The MIF file is now ready to be imported into MapInfo. However, when exporting data from Spotlight Pro version 5 (and all its modifications), another problem arises, which we could not get rid of. The fact is that in the process of exporting object level values, they are “scaled”. That is, the level value assigned when digitizing an object in Spotlight changes as a multiple of the scale selected when specifying the coordinate system (let me remind you that in our case the scale was set to 1:25). It turns out that a horizontal line with a level of 75 meters after export will be located at a level of 3 meters.
Such information is recorded in the MID file (Fig. 12). The third column of this file contains the level values to be corrected. We correct them in Microsoft Excel, but we have to save the corrections by juggling formats and vigilantly ensuring that commas remain as separators and periods as decimal separators. If anyone can suggest an easier way, write to the author by e-mail [email protected], I will be very grateful. For AutoCAD users faced with this situation, the only advice I would suggest is to specify an increased value when setting the object level in Spotlight. This is quite inconvenient, but correcting the level of each object from AutoCAD is even more inconvenient.
Representatives from Consistent Software reported that this problem has been resolved in the sixth version of Spotlight Pro. The English version of the version is already ready, all that remains is to wait for its Russification...
The last final stage of digitization is the mapping of natural land objects.
21. Quarters: Forests
. Layer: Quarters
. Object type: FORESTS
. Localization: area
. = 1:5.000
. : describing spline, double line of a given thickness (for forest belts)
. Application order: applied after the object RAILWAYS
The definition of forests is simple: everything that is not gardens is forests. In other words, trees that do not grow in the courtyards of a populated area, and do not constitute horticultural plantings - forests.
Forests are often found on the borders of populated areas, but can also be found in their centers near uninhabited areas, rivers or ravines.
By analogy with gardens, forests are digitized using describing splines at a scale of 1:5,000.
It is necessary to distinguish between forest and bush. The shrub is characterized by low height (small shadows) and increased tenderness. The decision on which object to digitize the bushes remains with the cartographer: if a bush clearing is surrounded by a forest, it makes sense to merge it with the forest, if there is no visible meadow and forest around it, you can not select it, and digitize it as a meadow too. The picture on the left shows trees, the picture on the right shows bushes:
There is a certain minimum volume of plantings that must be digitized. Usually this is a group of 5-10 trees. Single trees should not be digitized (the same rule applies when digitizing GARDENS). Groups of trees located at close distances should be combined into a single array:
Trees are often found in the form forest belts- planting along roads and between fields. Forest belts should be digitized using the “double line of a given thickness” tool - the result will be elongated areal objects with rectangular edges:
Sometimes it happens that a dirt road “dives” into a forest belt, and “emerges” back only at its end. Such primers can be laid at random directly on top of trees. Usually from the “entrance” to the “exit” they walk along the edge of the forest belt:
Often found in large forested areas clearings, which is digitized by the corresponding linear object directly on top of the FOREST:
Please note that in cases where a paved road passes through a forest, at the stage of final processing of the map, mutual overlaps between the FOREST and ROAD ROADS objects will be eliminated.
Be careful when digitizing roads and clearings in the forest: they are difficult to see behind the trees. There are no dead-end roads in the forest: not a single road in the forest usually ends just like that. Each of them either leads to a river, or to the other edge of the forest, or flows into another path.
Sometimes in large forests there are “clearings”: clearings or felling, surrounded on all sides by forest. Such clearings should be digitized using MEADOW objects (see below), and then cut out from the forest using the “Create a subobject by copying” command from the “Cutting and Stitching” toolbar:
Advice: if the GIS Map is “buggy” and the “Create a copy subobject” command does not work, cut the edited FOREST object into two parts with the “Dissecting the object with a line” command, across the MEADOW object. After this, you can cut out the MEADOW from both halves of the FOREST with the “Dissecting an area object with an object” command, and then glue both halves of the FOREST back together.
22. Soils: Arable lands
. Layer: Soils
. Object type: ARRANGEMENTS
. Localization: area
. Recommended digitization scale = 1:5.000
. Recommended application method: smoothing spline
. Application order: applied after the FOREST object
Arable lands are large areas of cultivated land for agricultural purposes.
The main difference between arable land and vegetable gardens is that arable land is not divided into small private plots, but is a single whole field.
The arable land in the photographs can be of many colors: it can be absolutely black freshly plowed land, bright green winter crops, and yellow, almost gray spring crops. The main visual feature of arable land, which allows it to be distinguished from meadow, is the monotonous parallel furrows, clearly visible at a scale of 1:2,000:
In some fields, tractor furrows can be so bright that they can inadvertently be mistaken for dirt roads. Don't be fooled, these are not roads, these are arable lands:
The arable land should be digitized at a scale of 1:5,000 using the smoothing spline tool. For better smoothing control, it is recommended to specify at least 2-3 points at each corner of the field. Digitization should be carried out along the edge of the plowed land, at a distance of 5-10 m from forest belts and roads .
Sometimes there are situations when the forest belt is close to the arable land. Arable land may be placed on top of such forest belts, bearing in mind that at the stage of final processing of the map, the overlap of these objects will be eliminated. No restrictions apply to blocking arable lands and dirt roads:
Sometimes among the arable lands there are uncultivated areas of a round or tongue-like shape - these are swamps and ravines. They were discussed in detail at the beginning of the current chapter:
23. Soils: Meadows
. Layer: Soils
. Object type: MEADOUS
. Localization: area
. Recommended digitization scale = 1:5.000
. Recommended application method: describing spline
. Application order: applied after the arable land object
Meadows are an area where there are no trees, arable lands, rivers or swamps, no buildings, no roads - there are no traces of human activity. A meadow is an area where grass simply grows. From the point of view of central Russia: a meadow is where there is nothing.
Of course, such a territory can be left empty on the vector map. But when digitizing maps, it is considered bad form to leave large areas empty.
For example, small empty spaces between arable land and a forest belt, between a forest belt and a road, reaching a maximum width of 15 meters, should not be designated as meadow:
But a clearing measuring 150 m in diameter must be designated as a meadow:
Digitization of the meadow area is carried out with the “describing spline” tool, in one of two ways (or a combination of them):
Leaving a 5-10 mm gap to objects (for example, to the road)
. by overlaying a meadow on top of area objects (forests and rivers) so that its boundary is strictly inside the intersected object, and then using the "dissect area object by object" tool to match the boundaries.