For in-house use, our mapping software is Topo USA 6.0 by DeLorme. This software package includes a built-in USB interface with the the Earthmate PN-20 GPS receiver as well as a built-in internet link to DeLorme’s server. This gives the user the ability to download map data from DeLorme (pay as you go) and then create custom map packages from which to build your map project or for use in the field after uploading to the PN-20. Following a day of exploration, recorded tracks and waypoints are downloaded from the PN-20 to a PC and added to the “master map.”

Map packages uploaded to the PN-20 may consist of up to four layers: Topo USA vector-based topographical data, scans of USGS topo maps (raster data), color satellite imagery (limited utility for our purposes), and b&w aerial photography. The former is provided along with the initial software purchase and the latter three types of data are purchased and downloaded incrementally in multilayer packets.

One of the more impressive features of this software is its ability to display all four types of data in 3D. 3D maps can be panned, rotated, scaled up/down, and viewed from an angle anywhere between 0 degrees (looking towards the horizon) and 90 degrees (straight down from above). This is a big help in visualizing the terrain and determining where a railroad might or might not have been feasible.

The enormous drawback to this software is that they absolutely refuse to reasonably let you use maps generated by the software. For example, if we wanted to put them on this website, we would need signed releases from Delorme, and they’d probably want payment. For that reason, we use GPSvisualizer.com to generate overlays of our GPS tracks onto USGS topo maps. We also may experiment with creating interactive Google maps in 2010.