GPS.LSP

Well, I think it is about time for my second post here.  I really enjoy the outdoors, and have been doing quite a bit of hiking with a GPS I got a couple years ago.  I have been using some software with detailed topo maps for plotting courses and uploading them to the GPS for most of the hikes, but have found some limitations with this.  First of all, while the maps are highly detailed in respect to terrain, they are in some cases decades old and the backroads have changed considerably since they were printed.  This can make road navigation difficult and at best a guessing game.

There are all kinds of other maps available, some of which show excellent backroad detail, but they are not available in electronic format compatible with any GPS software that I have been able to find yet.  This is where GPS.lsp comes in.

In order to make the most out of these maps with a GPS, I wrote a routine that when a electronic map (whether scanned or other) is imported into AutoCAD and scaled and stretched accordingly to calibrate it, you can draw a polyline on the route you wish to take and run GPS.lsp to export that route as either a CSV or GPX type file that is compatible with may GPS interface pieces of software.

First a suitable map must be found, and scanned to an image file.  You may then insert this into AutoCAD as a raster image.  It is important that the map has a lat/long grid so that you can use it as a reference when calibrating the map.  You have to scale and stretch the map so that your crosshair position corresponds to the exact lat/long shown on the map.  Sometimes this may also require a rotation so that lines of longitude run straight up and down.  You can see a typical map here I am using as an example.   Notice in the bottom left the cursor position is showing as a lat/long value.

 

Now you can see in the second screenshot that I have drawn a green polyline over a section of the Island Highway to use as an example of a route.  It is simply a case now of running GPS.lsp, specifiying a file type and location, and clicking the polyline.  The file it askes you to save is a text file that comprises a list of points that make up your polyline route.  The GPX or CSV file will be saved in the same directory you specify for the text file.

The last screenshot here is the GPX output loaded into Google Earth.