Traffic on the Golden Gate Bridge (USAPhotoMaps Urban Area Mode)

USAPhotoMaps™ retrieves TerraServer aerial photos, topographic maps, and urban area map types (below). The freeware program from JDMCox Software also displays elevation data, place names, USGS landmarks, TIGER (US Census) roads, road names and your own GPS data. It is one of the fastest tools available for navigating to any location in the United States and collecting TerraServer image tiles for base maps. Assemble image tiles into single, georeferenced base maps that can be opened by geospatial programs or drawing programs. Use USAPhotoMaps to quickly get latitude, longitude or UTM coordinates for any position. GPS waypoints, routes and tracks can be created and displayed as map overlays and transferred to or from GPS units.

Photo (P)	Topo (T)	Urban (U)
You can switch between the three map types by tapping P, T or U on the keyboard. Part of the San Francisco-Oakland Bay Bridge is shown above. At the closest zoom level, grayscale photos are 1-meter resolution, topographic maps are 4-meter resolution, and the color urban photos get really close as shown by cars on the bridge (left) at .25 meter per pixel resolution. Urban area coverage is limited to the dark blocks in the map below.

USAPhotoMaps comes packaged with an installer that unzips the program and places a shortcut (below) on your desktop.

Start USAPhotoMaps and begin the process of image retrieval by choosing a location. The simplest approach is the GoTo utility from the menu bar, which gives the following options:

• The Address option requires at least a city and state or zip, but it can take you to a specific street address.

• The Populated Place and USGS Landmark options require additional data files from the USAPhotoMaps site. If you use this feature and the data files are not present, USAPhotoMaps will retrieve and copy the files to your PhotoMaps directory. The initial download may take a few minutes. Once installed, you can zoom straight to your destination by selecting it from an alphabetical list.

• The Lat/Lon option, similar to the File>New Map Location menu below, asks for an initial latitude/longitude or UTM coordinates for your project. For the Lat/Lon, you can use decimal degrees or enter degrees, minutes and seconds.

After you click OK, the screen will first display a grid of gray, blank placeholders. Click on "File>Download Map Data>Fill Screen" (or tap "F" on the keyboard), and the tiles begin to fill in.

You can scroll the screen with the arrow keys on your keyboard or zoom out (Page Up key) and ask the program to again fill the screen (tap the "F" key). Zoom in again with the Page Down key.

How long does the download procedure take? If you want an image about 4.5 square miles square (about what you'd fit on a computer monitor at 1024x768 resolution when the zoom is set to four meters per pixel), USAPhotoMaps will retrieve approximately 1.6MB of data. At 1-meter resolution, 280 TerraServer tiles are downloaded. With an Internet connection receiving data at about 30KB/second, it takes a little less than one minute to download the images. The process is smooth with a broadband connection, but some people may experience hang-ups if they are using a slow modem.

TIGER Roads

Aerial photos clearly show roads and streets but not road names. Use the File>Download Map Data>Tiger Streets command (shown above, or tap S on the keyboard) to solve that problem. USAPhotoMaps presents a list of states and counties. Pick the one for your area of interest, and the required data will be downloaded and saved to your PC. Use the command View>TIGER Streets to pick the type of road layer to display. Move your mouse over a road node to view its name as shown in the example below:

If you want to use the downloaded images in a geospatial program like fGIS, Map Maker or Global Mapper, you'll need to use the procedure described below to merge the tiles and generate a GIS World Coordinate file. NOTE: TIGER roads or elevation lines are vector objects which are not saved when you use the following "Create BIG jpeg file" tool.

Merging Images with USAPhotoMaps

	USAPhotoMaps includes a utility to "Create a BIG jpeg file", found under the File menu. It will assemble the image tiles downloaded by USAPhotoMaps into one georeferenced image. Just drag a bounding box on your screen with the PC mouse, and the tiles will be combined into one image file ending in "jpg" and an accompanying "world coordinate file" ending in "jgw".
	The program will save the two associated files to the USAPhotoMaps folder on your PC. The file names like the example on the left are based on the UTM coordinates of the top-left corner and the UTM zone number. You might want to move two "jpg" and "jgw" files to a project folder. Rename the files if you wish, but make sure the first part of each file name is identical (such as Camp_Douglas.jpg and Camp_Douglas.jgw). That way, mapping programs can find the world coordinate file associated with the image.
The world coordinate file from the preceding process would look something like the following if you were to open it with a text editor: Click here if you want to know what each line means. Since the names of the map coordinate system and datum are not part of the world coordinate file, many mapping programs will need you to provide that information. TerraServer aerial photos and topographic map images use the Universal Transverse Mercator (UTM) projection and the NAD83 datum. You'll also need to provide the UTM zone number. Using the world coordinate file and the name of the projection/datum/zone, mapping programs can correctly position the image in relation to other geographic data. If you need to change the projection of the image to some other coordinate system, see the Digital Grove tutorial on GDALWARP. fGIS and HyperCube can also be used to warp a TerraServerUSA image to another projection.

Using USAPhotoMaps with your GPS Unit

If you have a GPS Unit, USAPhotoMaps can connect to it and display your waypoints and tracks directly on TerraServer images. The program will work with any brand GPS receiver as long as it comes equipped with a serial cable (or USB cable for Garmin units) for the PC and supports either a Garmin or NMEA protocol.

You will need to set up USAPhotoMaps so it can find where your GPS unit is connected and so it knows what transfer rate to use. That may require some trial and error. See the GPS Help in the program.  

Select GPS>Track>Receive, and the track points will be saved as a file and displayed as a poly-line overlay on the photo as shown below. Waypoints can also be received and displayed in a similar manner.

Another very useful feature of USAPhotoMaps is its ability to send waypoints to your GPS unit. Say you want to explore a parcel of woodland, and you'd like to know when you are getting close to the corners of the property when you are out walking around...

As you navigate with the GPS unit in the field, you will be able to use the corners that you marked and sent as reference points. If you have downloaded elevation data with USAPhotoMaps, the GPS points that you send to your GPS unit with USAPhotoMaps will include USGS DEM height data.

If you can't pick out the points you want to transfer from the aerial photo, you can switch the view to the topographic map option:

The topographic map view provides section lines and other reference marks that might be clearer than on the aerial photos. The resolution of the topo maps is limited, however, to four meters per pixel as compared to one meter per pixel maximum for the aerial photos.

Adding Elevation Data

USAPhotoMaps can retrieve elevation data from the USGS and add it to your project. First, use the File/Download Map Data/Elevation Data command (below).

Instructions that appear will ask you to click on the tiles that you want elevation data for. The program downloads the information and will display contour lines as shown below if you turn them on (tap "C" on the keyboard). Zoom in to see the lines.

Another useful feature of USAPhotoMaps is retrieval of the date imagery was produced. Find the date tool under the Help menu.

Real-Time Location Display

If you travel with a GPS unit and laptop PC, USAPhotoMaps can display your real-time track on a photo or topo map as you move. Simply connect the GPS unit to your laptop PC via a serial cable, start USAPhotoMaps, and select "GPS>Show Location".

If you plan to use the program in real-time, download or transfer your background image tiles to the laptop or a CD in advance. The "USAPhotoMaps.txt" file that comes with the program explains the procedure for saving image tiles to a CD. Take care when you are in a moving vehicle to watch the road, not your laptop screen.

Download USAPhotoMaps and Data Sets

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