GPS and TOPO map Information
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Here is a collection of the information concerning my use of GPS and electronic mapping software. | |||
| 1 - My Setup - TOPO! and GPS | 4 - Using TOPO! with other Software | |||
| 2 - Distance Accuracy on Long Trips | 5 - Google Earth | |||
| 3 - The Side-Hill Effect | 6 - Links | |||
My Setup - National Geographic's TOPO! Software and GPS
Throughout my website you see references to TOPO! files, maps and elevation profiles. This is a quick guide about TOPO! and the GPS setup I have to interface them together.
TOPO! is a topography software package that has all of the USGS maps on CD. The software allows you:
| View, print, and export maps at different scales | |
| Draw routes and make annotations | |
| Determine how long a route will be as well as how much climbing and descending you will have to do. | |
| The software will interface with a GPS to import and export waypoints and routes. |
I have a very small GPS unit that I take along on rides I have never done before or that I have not gathered trail data on before. I rarely use it to navigate by, I mainly use it to log my location every few seconds thereby making an electronic breadcrumb trail. When I get back to Casa de la Bill, I hook up the GPS to the computer via a serial cable and download the data right into the TOPO! software. Now my breadcrumb trail is right on the map. After making annotations about the trail on the map, I save all of the data as a TOPO! file. I can now call up the map and data at anytime. This is the file that I post on my website that anyone can then use.
NOTE: Since I first started using TOPO! there have been some free updates provided for the software. One of those updates requires that old versions of the TOPO files be updated to the new format. There is a mixture of both formats on my site. I will be updating to the new formats as I update the trail maps. I have noticed that the conversion only work if you open up the TOPO program first and then open the data file. Double clicking on the data file to open the program does not do the conversion properly.
So you want to do this stuff: You can pick up most of this stuff at REI.com
for a pretty good price. I'll also mention some other sources when that have a good deal.
| Get the software. I use TOPO! California Edition which runs about $99.00 | |
| Get a GPS - The basic Garmin eTrex will work fine for most people. They offer
about 6 different models with varying levels of features and cost. All
of them weight only 5.3oz (not including the 2AA batteries) and fit
easily into the palm of your hand and the controls are designed for the unit
to be operated with one hand. I am currently using a Garmin Vista Cx which has the nice features like being able to up load topographic maps as well as an altimeter or a bunch of other goodies. I also highly
recommend getting a neoprene case.
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| Get an interface cable - You can buy the really expensive cable from Garmin for about $35.00 or you can by an after market cable from www.gpsconnection.com for about $22.00. GPSconnection also sells on eBay so you may be able to get it for even cheaper through an auction. | |
| Optional handlebar mount - I personally do not have one, and I have heard mixed reviews about there use. I modified my neoprene case to allow me to strap it to my handlebar. The eTrex series has an internal antenna and sometimes in densely forested areas I will lose track under the canopy. Having the GPS on your handlebar does not help in areas like this as your own body will have assist in blocking the GPS's view of the sky. I normally clip mine onto the back of my Camelbak so that it always has a good view of the sky. Handlebar mounts run about $22.00. |
Distance Accuracy with long trips with a lot of elevation changes
When you download GPS data to the TOPO! software or if you freehand draw a route
onto the map the mileage reflected by the software does no account for the
distance you travel up and down. It computes and reads the elevation
changes, but it does not account for it in the mileage. That is why your bike computer will always
indicate more mileage than you GPS or the TOPO software. On a fairly flat or a
short ride this difference is negligible. However, as distance and
elevation change of a ride increases this difference can become quite large.
To get a more accurate measurement of the mileage shown on the map you have to do a little math. 
To the left is the elevation profile for the Black Star Canyon, Main Divide,
Silverado Loop ride that has both a lot distance and elevation changes. In
the lower left hand corner is the mileage readout from mile 0 to the mark were the
yellow dot is located. (The yellow dot is all the way to the right at the
end of this route). On the bottom right hand corner is the readout of the +
and - elevation changes. Since this is a loop ride the + and -
should be the same and they are real close.
Now the TOPO map says this is 25.20 miles long. Oh, I
don't think so. My legs will surely agree with my bike computer that is
more like 26.98 miles. So this is how to compensate for the elevation
changes. Add up both the + and - elevation
changes. 4480 + 4479 = 8959 feet. Now convert that to miles by
dividing it by 5280 (5280 feet per mile) 8959/5280 = 1.70 miles. Now we
can just 1.70 miles to 25.20 miles the the elevation profile is telling us and
we have a much more accurate number. 26.90 miles. Now there is
a .08 mile difference between the map and my computer.
But Bill, this really sucks to go through
all that you say! Well on all my reviews where this effect
could be substantial I have already compensated for it on my marks on the maps
and TOPO files as well in my trail descriptions.
If you have a long route that is predominately on the side of steep hill, your elevation profile for the entire trip can be wildly off. This is due to the fact that the Global Position System is usually accurate to within 30 feet. The next time you are out on a trail along a steep hillside and look at the difference in elevation 30 feet to your left and right. It can be substantial. Now couple this with a GPS that is logging your position every five seconds. This "acceptable" variance recorded every five seconds can add up to a lot of extra elevation changes. A good example of this is the elevation profile for the Santa Ana River Trail. There is maybe 3,000 feet of actual elevation change, but the profile shows nearly 6,000 feet. I usually point out in the description what the actual elevation change if there is a significant difference between the profile and reality.
Using TOPO! with other software
I have used most of the other popular consumer topographic map software packages on the market right now, and I still find National Geographic's TOPO! State Series to be the most user friendly and I prefer the maps over other products like Delorme's TOPO USA. One disadvantage to using TOPO! is it's lack of ease in interchangeability of data with other programs. There is one bit of software that you should really look at, GPSBabel. This is freeware that can convert to and from a myriad of GPS data formats. GPSBabel's capabilities when working with TOPO! files is limited to reading the waypoints, routes, and tracks and converting to other formats. This works well if you use some other program besides TOPO!
The easiest way I have found for getting track data into TOPO! (which shows up as the continuous trail plots you see on all of my maps) is by using your GPS as a "clipboard" for your data. Not all programs support uploading track files to GPS unit (TOPO! does not) so after looking at various free GPS programs that would both support track data uploads as well as some of the other common formats in use (GPX, KML, and KMZ), I settled on OziExplorer. As of version 3.95.4m, the free version could use both GPX and KML files and then upload that data as tracks to your GPS. Once in your GPS, it is a no-brainer to download the data into TOPO!
NOTE on intellectual property. I post my map files on my site to share and assist people in getting out and riding new places. Please do not download these files and then repost them elsewhere passing them off as your own data in either their original format or a converted format. If you would like to use some of my stuff email me, I'm pretty cool about it but I do not like being leeched. More Legal Stuff.
Google Earth is a really cool program which can really be handy when researching new places as well as sharing information. There are a ton of add-ins for Google Earth and it's intrinsic ability save plots/tracks and KML formats is extremely helpful. I bought the upgrade to Google Earth Pro (Its $20 a year) so that I could download GPS data directly to Google Earth as well as draw my own plots. As of July of 2006, Google Earth did not support uploading to GPSs. However, it is a fairly simple process to save your plots as a KML formatted file. Then using the OziExplorer software I mentioned about, you can directly open the KML file in OziExplorer then upload the data as a track file to your GPS. So the basic step to take something you have drawn or found on Google Earth and get it into your GPS as a track is:
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Save the plot as a KML file in Google Earth.
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Open up OziExplorer
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Load the World Map File (File>Load From File>Load Map>Select World.map) <Require to open a KML>
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Import the Google Earth File (File>Load From File>Google Earth (kml) File)
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Once the file is open, Click on either Garmin or Magellan from the Menu and select "Send Track to GPS".
(I'm assuming you figured out how to configure OziExplorer to use your GPS) -
Fire up TOPO! and import the track from your GPS.
(I'm assuming you know how to use TOPO! at this point) -
Look at your Google Earth track in TOPO!
Here is an example in which I used Google Earth and TOPO together. In May of 2006, I rode Iron Mountain, but forgot to bring along my GPS. When I got home I discovered that there was absolutely no trails shown on the USGS maps in TOPO! for Iron Mountain. However, the entire trail system was easily discernable from the aerial photo of Iron Mountain in Google Earth. I zoomed in and drew in the trail system as a plots in Google Earth. Once done drawing the trails, I save them as a KML file. I then opened the KML file using OziExplorer and uploaded the data as a track to my GPS. I then opened up TOPO! and imported it right into TOPO!
Please take a look at my GPS and Topographic Resources section of my links page for more information.
