website for topo maps (for GPS)

12:39 p.m. on April 5, 2010 (EDT)
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just wondering if there is a website or download site where you can find generic versions of the national park topo maps for garmin devicies..

Something with trails, but doesn't have all the POIs would be great!!

I just bought a new GPS unit for my upcoming hiking trip and I want to test it out before I spend all the cash on the Garmin Topo software!



2:01 p.m. on April 5, 2010 (EDT)
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Several of the geocaching groups have created maps of the parks in their local areas. So if you contact the group local to the area you want, you might be able to obtain them. One catch, though, is that National Parks, State Parks in some states, and some other federally-managed land areas do not allow geocaches. So the geocachers won't have wasted their time doing maps to put on GPS receivers for those areas.

This site might have what you want. should be aware that Garmin especially, but most of the GPSR manufacturers want you to use their proprietary software. If you read the fine print, loading other software will void the warranty.

Also, a huge disadvantage of GPSRs, especially the handheld units that backpackers use, have such tiny screens that even at the "overzoom" settings (zoom settings that are beyond the resolution of the stored maps), the maps are of very poor quality. The scanned 1:24,000 maps that Garmin, Delorme, and other GPSR manufacturers have available also are limited to the tiny screens, plus magnifying the view (the "+" or "IN" button on your unit, depending on brand) just magnifies the fuzziness of the scan.

Delorme has downloadable satellite and aerial photos (for an inexpensive annual subscription for unlimited downloads) that are scaled to the resolution, which you can switch between the photos and maps. These are restricted to their PN-30, -40, and -60 series GPS receivers, of course, though these are fine units that are in many ways superior to the Garmin units (I have never had a Delorme GPSR fail, but I have had Garmins fail completely - not battery, but the software - out in the field on a 3 week expedition in an area with no trails of any kind).

Because of the limited memory, the maps in GPSRs at most scales are vectorized rather than scanned. That is, a road, trail, contour line, shoreline, etc. is actually a series of points that the software connects together using an interpolation algorithm so that it looks curved at larger scales (large scale = looking at a large area; small scale = looking at more detail in a smaller area, the standard geographer and mapmaker definitions, which you will hear all wrong from a lot of sales people). One of the results of the vectorization is that the maps displayed on your GPSR are pretty crude and often downright inaccurate.

The bottom line is you need to always carry a hard-copy map and a compass, and learn how to transfer coordinates of a point between your electronic widget and map. That's something covered in the Finding Your Way course I give for the Sierra Club's Clair Tappan Lodge (June 11-13 is the next workshop).

Now, you can download USGS topographic maps for free from the USGS map site and print them out yourself - so the cost is your printer's electricity and ink/toner and the paper. However, these are the standard USGS quads as the various scales, and are not stitched. To get stitched maps (so you can avoid the "my campsite is in the corner of the map" syndrome), you need to use a computerized mapping program such as National Geographic's Topo! (my choice) or Delorme's Topo USA (my second choice, which I also have).

2:17 p.m. on April 5, 2010 (EDT)
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wow, thanks for the response Bill, very very interesting and it seems I have much to learn...

I always carry compass and a trails illustrated topo Map (National geographic i believe).

GPSR (i assume that is a handheld gps unit?)

My story behind getting a GPS.. got a extrex vista as a gift for Christmas last year, and I knew from reading that they are terrible. So I took it back to REI and got my 120 bucks back. They had a discontinued garmin GPS unit, open box, on cleareance and a 20% off coupon that I had got me a Garmin GPSMAP 76CSx for about $90. Which are still going for 300 bucks on EBAY. (i got this about a year ago).

My use for it is purely entertainment purposes, as i've never had one before and I would never put 100% trust into the unit. Last summer I was able to get within 10 feet of geocaches using this device (used for a summer work program w/ kids).

That being said, all I really want it for is to get a rough estimate of mileage between POIs, and just need software to get that done... I do not care about the warranty because if it doesn't work right REI will still take it back.

Thanks for the help!

7:15 p.m. on April 5, 2010 (EDT)
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"GPSR" = "GPS receiver", an electronic widget that receives the signals from the satellites ("GPS Space Segment") and processes them to determine the position of the GPSR's receiving antenna in 4-dimensional space (3 space and one time dimension).

To say "I have a GPS" implies that you have a full Global Positioning System, comparable to the NAVSTAR Global Positioning System (the US system), Galileo (the EU system), GLONASS (the old Soviet, current Russian system), or the comparable Chinese or Indian systems, complete with Ground Control Segment, satellites, and Users.

The 76CSx is a reasonably good receiver, with the largest screen of the handheld receivers. Contrary to what you read, the Vista is actually a pretty good GPSR, assuming you had one of the later models with the high-sensitivity chipset. Like the Vista, the 76CSx suffers from the same fatal flaw of having the built-in sensors for a magnetic compass (flux-gate compass in particular) and barometric altimeter. These are battery hogs and best left turned off. The compass is easily decalibrated, which is easy to overlook if you are in haste or in desperate need of getting a compass reading. The barometric altimeter, like all barometric altimeters, is dependent on current air pressure and how close the current atmosphere is to the "standard" atmosphere, the remedy being frequent calibration at known altitude points (a mountain pass, a lake with the surveyed altitude marked on the map, or better still, the GPS-derived altitude). The altitude the GPSR determines from the Global Positioning System satellite data is accurate (95%) to within 30 feet, compared to the USGS maps that are plotted to an accuracy of "1/2 contour interval at surveyed points), which generally means +/- 20 feet (40 foot contours are fairly standard in mountainous areas). If you have gone more than 3 or 4 hours, the barometric altimeter can be off by 200-300 feet, and in summer, climbing up or down a mountainside by, say, 2000 feet, can be off by a couple hundred feet (if you haven't recalibrated for a day or two, it can be off more than that). Unfortunately, you can not set Garmin "S" (for "sensor") GPSRs to display the GPS-derived altitude as the default - they only display barometric altitude (though you can briefly look at the GPS-derived value).

However, for your desire to get mileage between locations, the Track function will give that to you quite accurately, or at least the length of the path you followed. You do not need any maps beyond the base map that is already in the 76CSx. You can also reset the odometer display to 0 at the start of the hike and get an accurate value (to within a percent or so, which is much better than measuring off a map or using a pedometer). In the "numbers" page (where the odometer, speed, etc are shown as numbers), push the menu button, select "Reset", check or uncheck the values you want reset, answer "OK", and then go back to the main screen by clicking "PAGE" or "QUIT". Then just hike and read the odometer.

9:16 p.m. on April 5, 2010 (EDT)
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Damn Bill, you are good!!!

Thanks for the help, I definitely learned something new today!!


1:41 a.m. on April 7, 2010 (EDT)
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I have the same unit - the 76CSx. I got a free map of CA from here-

Plus some good info on how to download it from the forum.

11:15 a.m. on April 11, 2010 (EDT)
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is there a GPSR 101 thread on here at all? The basics and such?? Or should I just read that damn manual?? =)

1:57 p.m. on April 11, 2010 (EDT)
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There have been lots of threads about using the widget. Plus, I am slowly writing a "basics" article for Trailspace.

But for now, I suggest going to, looking at the "local" listings, and checking in on your local area geocaching group.

OR ---

If you happen to be in California, I am presenting a land navigation workshop for the Sierra Club's Clair Tappaan Lodge at Donner Pass the weekend of June 11-13. The formal part is Sat and Sun (12 and 13 June). You do not have to be a Sierra Club member to take the course, though you get a reduced price for the meals and lodging at the lodge (3 meals included, and the chef is a really excellent cook).

I think the formal title is "Finding Your Way". It starts with the basics of finding your way with nothing in hand, goes to maps, compass, altimeters, and ends on with a half day on GPSRs. It is very much hands-on, with a bit of hiking around in the woods (so wear your hiking boots). I will have some loaner receivers, and I will demonstrate some computerized map programs.

The full information is on the Clair Tappan Lodge page of the Sierra Club website. The cost of room and meals is pretty inexpensive for that area, with the meals being plentiful (I always gain weight when I spend a weekend at CTL). The area is beautiful, so bring the family so they can wander through the woods while you are staring at the GPSR screen. Lots of birds, probably still flowers, maybe even some snow this year, given the huge snowfall (another foot or two this weekend).

I should post a full notice about this course somewhere here on Trailspace, since people do ask frequently where they can learn to find their way in the woods and hills.

7:59 a.m. on April 12, 2010 (EDT)
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There have been lots of threads about using the widget. Plus, I am slowly writing a "basics" article for Trailspace.

Yes, yes, please do, Bill!

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