*** Garmin GPS Units for Search & Rescue *** From Search & Rescue Info: : We are looking for GPS units for search & rescue operations - : which means they should be rugged, reliable, easy to use, have long : battery life and - most importantly - work under a forest canopy! : We have looked at the Trimble Scoutmasters and are considering the : Garmin 45. : Does anyone have any recommendations on these or other units? : Thanks, : Martin Colwell : sarinfo@mindlink.bc.ca To: Search & Rescue Info Date sent: Thu, 25 May 95 14:54:04 -0800 From: BUECHER, ROBERT H. Subject: GPS experience for SAR To: sarinfo@mindlink.bc.ca Hello, I saw your posting asking about what type of GPS to use for SAR. I'm a member of Southern Arizona Rescue Association, an MRA team in Tucson, Arizona. There are about 5 of us who have bought either a Garmin 40 or 45, mainly for use in search & rescue. I don't have any hands on experience with other types of GPS but I can tell you how the Garmins have worked for us. What is important to me is that it be small and light and have long battery life. The Garmin 40 & 45 both fit into a shirt pocket which makes them very convient to use, no digging through your pack and there is little concern about a heavy or bulky piece of equipment. Battery life is 10 to 20 hours on 4 AA batteries. I also like the one handed operation of the Garmin, almost operation can be done with the thumb. Also the light for night use is very good, I wish my radio had as good a light. One drawback to the light is that the keys are not lighted and so you have to "know" them by touch. I do like being able to store 250 waypoints, I have only about 150 so far and still collect more. It's important to be able to add a name to the waypoint so you can tell what it stands for. Garmin lets you use up to 6 characters which is just barely enough. The Garmin also lets you have up to 20 routes of 20 waypoints each, a nice way to organize the waypoints. Something that I thought would be useful is the "track log" feature of the Garmin 40 & 45. When this is on it saves a graphical trace of your route on the display. The track can have up to 768 points in it and, with the proper computer program you can download the "track" as a series of location points with the full precision of the GPS. I thought that this would be useful on long searches where it is important to know what areas have been covered. You could printout a copy of the track to the same scale as the topographic map to get a quick plot. Garmin charges $150 for their computer program but there are several free programs for IBM & Macintosh computers that are much better. You may also want to look into what map datums are supported. The Garmin's have over a hundred different datums to choose from, some other GPS have only WGD84. Most of our topographic maps are old enough to be on the 1927 North American datum. There can be up to several hundred feet of difference between map datums. I'm not sure but I think that some of the other cheap GPS units have only *ONE* map datum. I would think that having lat/long on the same datum as your maps and also UTM would be helpful. One drawback to the Garmin is that it will not work at speeds above 100mph, so it won't work in a plane or helicopter. Speaking of which you might want to find out just how your local helicopers navigate. We found that the most useful way of giving our location to the helicopter was as a bearing and distance from the local airfield beacon. I think that most of your decision will depend on how you plan to use the GPS. If you want to track your every move then the performance of the antenna will be very important. If you need to get spot locations then you can almost always find a big enough clearing. I've found one of my biggest uses is as an aid to getting to unfamiliar locations. Just driving to the proper location is sometimes a problem. I like the Garmin 45 because I can mount the detachable antenna outside my truck and get better reception. You might also check to see how you will use the position information in the field. It is very difficult to plot a precise position on a map at night, in the wind, in the rain. We also discovered that the map which we use of a local mountain range did not have lat/long on it! (actually its a map that we print for our own use and never had a need for lat/long before now. We also discovered that our base camp was not perpaired to locate us on a map. In many cases it was faster to "triangulate" your location by giving a distance from two or more mountain peaks, or to give a straight line distance from a trailhead. Don't expect the elevations to be very useful, they can fluctuate by 200 to 300 feet. I find that my barometric watch/altimeter is more useful. A quick fix with the GPS can be up to 500 feet off. There can also be some problems in narrow canyons where one wall will act as a reflector. So far we haven't come to any firm conclusions as to how useful GPS really is yet. But the cost is cheap enough that its worth getting one just for the experience. Would I buy one again? You bet! P.S. We don't have a lot of trees down here so my experience in heavy forest is somewhat limited. (We do have forests up in the mountains above 7000 feet and I haven't had much trouble with my Garmin so far.) You might want to see that the GPS you buy has both true bearings & magnetic bearings. On the Garmin you can toggle this feature and it has magnetic declination already figured out for anywhere in the world. I don't know if all the GPS models have this or not! Bob Buecher Thu May 25 09:31:40 1995 Letter : 4664689 From: Tim Hogard Address : thogard@bridge.com Subject : Re: GPS units for Search & Rescue - any comments? To: sarinfo@mindlink.bc.ca (Martin Colwell) I just obtained a G40 and it seemes to have real problems sometimes but I don't know if its trees or buildings. These things lock on fast only if they have been off for less than a half hour. Your best bet with them is have them stored so they can get power and see the sky at all times and then when you need them, unplug it and take it away. When your done with the rescue operation, change the batteries, plug it in to a wall transformer and wait till you need it again. I don't know how tall your trees are but an idea... Get a very long telescoping antenna (like for an fm radio) I have seen one of these that was like 25 ft tall. Attach some velcro on the top and stick the G45 antenna on it. It might just work. - Tim Hogard --------------------------