Tutorial 1a – Using the Digitizer
Goals for this section:
- Download and save aerial imagery from TerraServer.com
- Digitize Lines, Points and Areas
- Save your GM8 workspace
- Export a .MP file for compilation with cGPSMapper
- Download the compiled .IMG file to your GPSr with SendMap20
Let’s get started.
GM8 has the ability to load and display overlays concurrently. This means that you may have a reference map loaded in a raster overlay, from which you can trace or digitize features in a vector overlay. We’ll begin the tutorial sequence working with both types of overlays.
Let’s see what data we can find online for Jackson, Wyoming.
I performed a Google search for ‘Jackson WY map’ and found this useful hand-drawn map in PDF format at
This is a typical tourist map showing local areas of interest. It’s clearly not to scale, and it appears to have been drawn with perspective to emphasize the nearby mountains. But it has lots of local detail that we can use. Open this PDF file in your browser.
GM8 offers a direct connection to online imagery. Click File | Download Online Imagery/Topo Maps. Select DOQ TerraServer as the source, and in Select Area to Download, specify Within 1 mile of address Jackson WY.
GM8 will download your requested aerial imagery, centered on Jackson WY.
While we’re waiting for the imagery to download, note that certain areas of the US have higher resolution color imagery available, and that data from NASA’s Shuttle Radar Topography Mission is available for the entire world. GM8 makes it very easy to locate and download useful reference imagery for your mapping projects. Google Earth is another very useful resource.
Let’s digitize a few features. The best working arrangement is to be able to see both the PDF tourist map of Jackson and the Global Mapper window at the same time. If you have two displays on your system, use them! If not, I suggest arranging the two windows stacked above and below, since the maps we’re working with are oriented similarly in landscape mode.
First, we need to establish a reference point between the two maps. We’ll find highway 89 and trace its route through town. In the aerial image, there is a large clear area shown just left of center, SW of the ‘Jackson WY’ dot, which appears to be the Teton County Fairgrounds. In GM8, press Alt+Z to switch to Zoom Mode, then click and drag over an area including Highway 89, the fairgrounds, and the Town Square, next to the ‘Jackson WY’ dot.
Referencing the PDF map, we can see that Highway 89 enters from the SW, turns east into town, then exits north just before the Town Square. We’ll trace this as our first road. Press Alt+D to switch to Edit Mode, then right-click and select Create New Line Feature from the pop-up context menu. You are now in the line creation mode.
Click at the point where the highway enters the aerial image on the west side, then move the cursor to the point where the road curves, and click again to add a vertex. Continue tracing the road until you reach the intersection at the SW corner of the Town Square. At the point where you want to place your last vertex, right-click. Right-clicking ends line creation, and brings up the Modify Feature Info dialog box, allowing us to name the feature and specify its type.
In the Name box, type ‘89’. In the Feature Type drop-down, select Major/US Highway. Click OK to exit the dialog. Your screen should now look like this:
If you do not see black dots representing the vertices of your road, press Shift+V to toggle the vertex display mode.
Referencing the PDF map, notice that highway 89 heads north out of town at this intersection. We will draw another road segment for this piece of highway 89, then join the two.
Position the cursor near the top of the screen where you completed the previous line segment. The cursor turn into an up arrow, indicating that by clicking you will scroll the screen. Click a few times until our Highway 89 road feature is at the bottom of the screen. If you haven’t pressed Esc or switched to another mode, you are still in Line creation mode.
Click at the last vertex you drew, then begin a new line going north out of town.
Advanced user tip: If the cursor turns into a down arrow at the point you want to click, press and hold the Shift key while clicking to override the scroll function.
Move the cursor up to the point where the road curves NE, and click to add a vertex. The road will continue off the screen, but your cursor will change to an up arrow. Click while the up arrow is shown, and the display will redraw, leaving you in the line creation mode. Continue drawing the road until you get to the edge of the aerial image. For your last point, right-click to terminate the line. Name the road ‘89’, the same as the other road segment. The same road type you specified for the first road segment, ‘Major/US Highway’ is already specified, so simply click OK to complete describing the Feature Info.
Press Home to show your entire project. Your screen should look like this:
Press Alt+D to enter Edit mode. Click the first highway 89 segment you created, then hold the Ctrl key while clicking the second segment to create a multiple selection. Right-click and select Combine Selected Line Features. If a dialog pops up informing you of potentially conflicting feature values, click YES to combine features. Press Esc to exit Edit Mode. Your single line feature for highway 89 through Jackson WY is now complete. Double-clicking the line brings up the Modify Feature Info dialog if you want to make any changes after the feature is defined.
A brief discussion about labels
Your Garmin GPS receiver (GPSr) has the ability to display road names in upper and lower case, or use accented characters … but not both at the same time. It is important to understand this constraint early in your map design process. This constraint does not apply to city names or area features, only line features like roads and boundaries. If you are quite certain that you will not need an international character set in your map, then you may use upper and lower case in your road names. By default, GM8 creates a header specifying to cGPSMapper that you are using the international character set, meaning that only upper case letters may be used for street and road names. For now, I recommend that you accept this default behavior, meaning that your street names should all be specified in CAPS.
Now we’ll add some local streets. In the PDF map, zoom into the area around the Town Square. Note that the street continuing west from where highway 89 turns north is named Broadway. In GM8, press Alt+Z to enter Zoom Mode, then zoom to a similar area as shown in the PDF map. Press Alt+D to enter Edit Mode, then right-click to Create New Line Feature. Click on the vertex where Highway 89 turns north, then create a line extending east to the edge of the aerial image. When you get to the right edge of the screen, instead of clicking the right arrow cursor to scroll the image, press the right arrow key on your keyboard to scroll the screen. Either method works equally well. Right-click to terminate Broadway at the east edge of town where the road turns north.
In the Modify Feature Info dialog, enter ‘BROADWAY’ as the Name, and select ‘Residential Road’ as the Feature Type from the drop-down list. You may object that Broadway doesn’t really look like a residential street, but we’re not really concerned with making a distinction between types of city streets at this time. The key difference at this point is highways vs. city streets. ‘Residential Road’ is the built-in Global Mapper type matching the internal Garmin road types for city streets.
On the PDF reference map, note that Cache Street extends south from the Broadway-89 intersection, continuing past the baseball field until it stops. Add CACHE ST as a Residential Road.
The street running east-west below Broadway is called Pearl. It begins at Highway 89 on the west end, and terminates just past Gros Ventre Street on the east. Add PEARL AVE as a line feature. If you’re not exactly sure where the road ends, don’t worry about it. Welcome to digital cartography.
Let’s add a few more streets and then we’ll switch our attention to Point and Area features. Add DELONEY AVE running east-west just north of Broadway/89, and GILL AVE just north of Deloney. Just east of the Town Square add CENTER ST, running N-S between Gill and Broadway.
JACKSON ST runs north-south starting near the west end of Gill, south to Karns Ave at the NE corner of the fairgrounds. MILLWARD ST is the next N-S street to the east of Jackson. Note that at its southern end, Millward jogs slightly west before terminating, a detail which is not shown on the tourist map. Instead of following the line exactly, click once to define the northern end of Millward, skip over the jog and right-click to add your endpoint at the southern end of Millward. We’ll fix up the jog next.
Press Alt+Z and click-drag to zoom into the area of the jog. Press Alt+D to enter Edit Mode, and click on Millward.
Right-click, then select Insert Vertex Into Selected Line. Click at the corner of the jog. GM8 inserts a new vertex into Millward at the NE turn. Repeat at the SW turn, and you’ve fine-tuned Millward to match the aerial imagery.
Add FLAT CREEK DR running south from 89 on the west edge of the fairgrounds.
Add SNOW KING AVE running east from Flat Creek Dr past the southern edge of the fairgrounds, ending at Vine St at the west edge of the Snow King Resort.
Create VINE ST running north from Snow King Ave, curving NE then N, ending at Kelly Ave.
Karns runs E-W on the north edge of the fairgrounds. Note that it stops at Millward, then continues west one-half block south of that intersection. We’ll define Karns in two sections. Define the first section of KARNS AVE from Flat Creek Dr to Millward. Define the second section of KARNS AVE from Millward east to Vine St.
An important note about road segments
Earlier we defined Highway 89 in two segments and joined them into a single line feature. Now we have Karns in two pieces, but we can’t join them, because the street that connects them is already defined as Millward. It is important that any given road segment has only one name. This will be important when we add routing information. So think of it in the way that you would give directions to someone – “head east on Karns until it tees into Millward, turn right, then in half a block run left onto the continuation of Karns”.
Let’s switch our attention to some area features. We started with the Teton County Fairgrounds as our reference, so let’s make it an Area Feature.
Press Alt+D to enter Edit Mode. Right-click to select Create New Area Feature. Click your first point at the NW corner of the fairgrounds, at the corner of Flat Creek and Karns. Click on each of your vertices in the roads bounding the fairground, heading clockwise around the fairgrounds. Note that as your cursor approaches the existing vertices, it will snap to that location, making it easier to align your area image with existing features. Continue clicking clockwise until there is only one segment left, just south of the intersection where you began. Right-click to complete the Area Feature boundary.
In the Modify Feature Info dialog, name this feature Teton County Fairgrounds, and select ‘Misc. Manmade Structure’ as the Feature Type.
Miller Park is at the corner of Jackson and Gill. Beginning at the NW corner, click around clockwise to the first three corners to define the boundaries of Miller Park. GM8 will snap to the intersections making it easy to align the Area Feature with your existing Line Features.
Add the Town Square as a City Park.
Now let’s add some Point Features.
Press Alt+D for Edit Mode, then right-click to select Add New Point/Text Feature. In the center of the Town Square, click to add a Point Feature called Jackson, and assign its Feature Type to ‘City, 10k-50k’.
Albertson’s is south of the Highway 89 – Flat Creek Dr intersection. Click in the center of the large white building at this intersection to create a Point Feature. Name the feature “Albertson’s” and assign its Feature Type to ‘Shopping’. Press Alt+G to enter Grab Mode, then click and drag your map to the right to show the area west of Albertson’s and south of Highway 89.
Add the Point features Grand Teton Plaza and Powderhorn Mall, both with Feature Types of ‘Shopping’.
Add the Virginian RV Park with a Feature Type of ‘Lodging’. Add the Cowboy Village Resort and the Snow King Lodge as lodging features.
Our project is beginning to take shape. Let’s look at the structure of the project and save it.
Maximize your GM8 screen, then press Home to show the full project in your display. Press Alt+C to open the Overlay Control Center. You will see that there are two overlays in our project, the TerraServer DOQ aerial imagery, and ‘USER CREATED FEATURES’. User Created Features are everything that we’ve added to the map so far – Line Features, Area Features and Point Features.
Select the TerraServer layer, then click Hide Overlay to see just your User Created Features. Click the same button, now labeled Show Overlay, to show the aerial imagery again.
Click Close to dismiss the Overlay Control Center.
In the File Menu, click File | Save Workspace As. Navigate to your \SAMPLE MAP PROJECT\SOURCE\CITIES\JACKSON WY folder. In the File name box, type JACKSON WY, then Save. Your project workspace is now saved as JACKSON WY.GMW. The .GMW extension means ‘Global Mapper Workspace’.
Click Ctrl+U, which unloads the GM8 workspace.
To reload your project, click File | Load Workspace, or at the bottom of the File Menu, in the recently used file list, click JACKSON WY.GMW.
If your internet connection is slow or you’ll be working offline, you will want to have a local copy of the downloaded TerraServer data on your machine. Let’s save a copy now.
In the File Menu, click File | Export Raster and Elevation Data, then select GeoTIFF. In the GeoTIFF Export Options dialog, select 8-bit Palette Image (PackBits/LZW Compressed). This format offers the smallest file size with the best performance in GM8. Accept the default settings, and click OK. Save it in your \SAMPLE MAP PROJECT\SOURCE\CITIES\JACKSON WY\ folder as JACKSON WY.TIF. This export will take a few moments. When the save is complete, we can reload our project with the local aerial imagery rather than the live online data.
Press Alt+C to open the Overlay Control Center. Select the TerraServer overlay to highlight it, then click Close Overlay. Close the Overlay Control Center dialog.
Press Ctrl+O to bring up the File Open dialog. Navigate to the \SAMPLE MAP PROJECT\SOURCE\CITIES\JACKSON WY\ folder. In the ‘Files of Type’ dropdown box, select Supported Commonly Used Types. Select JACKSON WY.TIF. The local copy of the aerial image loads. Press Alt+C to open the Overlay Control Center, and you’ll now see that JACKSON WY.TIF is shown as the first overlay. Press Ctrl+S to save your workspace using your local copy of the TerraServer aerial image. Press Home to zoom your workspace to show the entire project.
Now let’s have some fun and show off some of GM8’s real power. Click File | Download Online Imagery/Topo Maps. In the Select Online Data Source to Download dialog, select United States Elevation Data (NED) (30m Resolution). In the Select Area to Download section, select Current Screen Bounds. The elevation data loads on top of the aerial imagery, but behind the User Created Features. Let’s move this overlay to display behind the aerial imagery. Press Alt+C to open the Overlay Control Center, then right-click the Elevation Data overlay. Select Move Selected Overlays to Top of List (Draw First). Click Close to exit the Overlay Control Center.
In the menu bar, click the 3D button at the right edge of the control icons. GM8 renders a perspective 3D view of your project, combing the elevation data we just downloaded with the aerial imagery and our User Created Features draped on top. Click and drag in the 3D view to rotate the image. Pretty cool, eh?
Later in the tutorial we’ll use this elevation data to create contour lines in our map. But first, let’s save the data for offline access.
You may have noticed that the loaded elevation data is slightly larger than our aerial imagery, due to the different tiling sizes of the online data sources. We can crop the data set to match the aerial imagery before saving it.
Open the Overlay Control Center, then right-click on JACKSON WY.TIF. Select Create Area Features from the Selected Layer Bounds. Close the Overlay Control Center, and double-click in an open area of the aerial image. The Modify Feature Info dialog comes up for the Area Feature you just created. Note that it is auto-named to be the same as the feature it was created from, and that its Feature Type is Coverage/Quad. Click OK to dismiss the dialog. The Area is still selected, as indicated by a cross-hatch pattern.
Click File | Export Raster and Elevation Data, then select Export Global Mapper Grid. Select Feet as the Vertical Units, accepting all other default selections on the General tab.
Click on the Export Bounds tab, and select Crop to Selected Area Feature(s), and then OK. Save the file as JACKSON WY.GMG in the same directory. You can now close the live online overlay and reload your cropped .GMG file.
We don’t need the Area Feature covering the aerial imagery anymore, so let’s get rid of it. In the menu bar, click Search | Find By Name. Unclick ‘Lines’ and ‘Points’ so that only Areas are shown in the list. Select JACKSON WY.TIF then click Delete Selected. Close the Find dialog, and save your project.
Compiling your data
Next we will export our vector data in the USER CREATED FEATURES overlay in preparation for compiling it with cGPSMapper. In the File menu, select File | Export Vector Data | Export Polish MP (cGPSMapper) File. In the Polish MP Export Options, type ‘Jackson WY’ in the Map Name box, your name in the Copyright box, and accept all other default options. Save the Polish format file as JACKSON WY.MP in the same directory as your other data files for this project.
Now we’ll compile our exported .MP file. cGPSMapper is a command line program, meaning that is launched from a command shell. The simplest way to do this is to use a batch file, which we’ll create now.
By default, cGPSMapper is installed at
C:\PROGRAM FILES\CGPSMAPPER\CGPSMAPPER.EXE. The batch file we’re creating depends upon this location – if your installed location is different, adjust as necessary.
Open your text editor. Create the following single line, with the quotation marks:
“C:\Program Files\cGPSMapper\cGPSMapper.exe” “Jackson WY.MP” –o “Jackson WY.img”
Save this file in your data directory as MAKE JACKSON WY.BAT.
Open an instance of Windows Explorer (you can use the system shortcut keys
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