Poindexter

Well, if you don't want to elaborate, then don't bother trying to explain. My maps aren't "2deg diff form one side to the next", if you don't understand UTM zones then don't worry about it. Like I said, it's a preference thing. Some people like their moving map displays track-up, some like them north-up. Some work with bearings on their topo maps using true, some magnetic. Poindexter

RossOlson wrote: "Take a flat map of the country" In what projection? There really is no north pole on a mercator projection and if your talking about a conformal projection, then what do you mean by drawing a line "straight up"? I use true north many times to physically orient my topo maps to compare features on the map with what I see around me. As for your other question, yes, the variation changes slowly but not as slowly as you may think. The topo map of the area where I live was last updated in 1979 and shows a magnetic variation of 8°30' and today it is 11°8' It currently changes about 4'/year. You should never use the variation from USGS topo's as many of them are quite outdated. Also, grid variation on these topo's can be as much as 2° near the edge of a zone while the grid line at the center of a zone is the same as true north. Poindexter

Writer, you said: However, if you are using a topographic map, why bother to convert to lon/lat? I didn't see where anyone was talking about converting to lat/lon. And I guess you could use those UTM coordinates on the cache page as long as you set your GPS's datum to WGS84 before inputting them manually and then set it to NAD27 to use with the topo map. Poindexter

Declination is the angle between true north and magnetic north and changes annualy due to the constant movement of the magnetic north pole, which is not located in the Hudson Bay. Declination has nothing to do with the differences between a "flat" map and a globe. Grid declination is the angle between grid north and true north. Whichever north you use is a personal preference and not related to using a "flat" map versus a globe. Sorry, but your just adding to the confusion. Poindexter

To get the exact distance and azimuth between two sets of coordinates, try this nifty little free program. http://www.mentorsoftwareinc.com/PRODUCTS/FWDINV.HTM Poindexter www.geocities.com/fairbank56

Brown Dwarf wrote: One way to check would be to drive a road that goes due east/west, and see what the gps compass says you are doing. Should be real close to 90/270 if the unit is giving you true bearings. You need to be at 50' or more away from your car to get an accurate reading from a magnetic compass due to magnetic interference from the steel and other ferrous metal of the car. Even metal framed eyeglasses can throw off a compass that you are using to "sight" a bearing. Poindexter

I didn't see where anyone in this thread was talking about using lat/lon with a topographic map. And you can't use those UTM coordinates provided on the cache page with most topo maps because those coordinates are for WGS84 datum and most topo maps use NAD27 so you still have to do the conversion. Just let the GPS do the conversion for you and make sure you know the datum of the topo. Poindexter

NADCOM doesn't give coordinate conversion. I agree with Dave54, the first time I used jeep.com, it didn't give an accurate conversion and I haven't used it since. For a good on-line Datum and Coordinate conversion applet, try Maptran. http://www.ualberta.ca/~norris/navigation/maptran.html Not very user friendly, but it seems to be very accurate. Always agrees with my GPS anyway. Poindexter, www.geocities.com/fairbank56

Dual-Lock. Sort'a like velcro, but much much stronger. I use this on the mount for the SPIII as well as my eTrex. I just put some on the dash of our cars and it's just a snap to move it from one car to another. This stuff is great. You'll find many uses for it. You can get it at Radio Shack (I think that's what Granmaster Cache was referring to "stickypad") but it's cheaper at Target. You can also of course, buy it on-line. Just search on Dual-Lock. Poindexter www.geocities.com/fairbank56

Try this excellent book called "GPS Land Navigation" by Michael Ferguson Here's a link to Amazon. http://www.amazon.com/exec/obidos/tg/detail/-/0965220257/qid=1040477722/sr=1-2/ref=sr_1_2/102-1747661-1972951?v=glance&s=books Not sure really what your asking for. Basically, you need a map with grid lines or lat/lon graticules and a suitable "roamer" for plotting your position on the map. You must know the datum of the map. Let your GPS do the conversion from one datum to another as well as from one coordinate system to another. Poindexter www.geocities.com/fairbank56 (map printing help page)

Just testing.

The epe your gps gives you is not a true indicator of how accurate your fix is. It is just an estimation based primarily on satellite geometry. When SA was turned off the epe on Northstar 941X gpsr's did not change. They still show epe's of around 300ft. The programmers never changed the bogus algorithim that determined epe. They should do away with that feature. It only confuses people. If a gps new how much in error the position is, then why doesn't it just apply the correction? Because it doesn't really know how much in error it is, it just gives you a best guess. Which is useful to some degree but too many people take it as an absolute figure. Poindexter

Here's a neat little program for doing the conversion when your not online. http://www.mentorsoftwareinc.com/freebie/FREE1198.HTM Poindexter, www.geocities.com/fairbank56

To completely freeze the liquid crystal material in these displays would require exposure to temps below -60°C for an extended period of time. There is a remote possibility of the breaking of the seal between the two pieces of glass where the liquid crystal material resides due to going from one temperature extreme to another but I wouldn't worry about it. Cold temps will cause the material to react slowly and the display to not be as sharp as normal. Poindexter, www.geocities.com/fairbank56

I use a laptop connected to my StreetPilot III for navigating to the parking area of the cache's but not for actually finding the cache. I use Microsoft Streets&Trips as well as USAPhotoMaps with topo maps and aerial photos that I am constantly downloading to the hard drive. I power my laptop from 12V via the cars accessory receptacle. Many laptops will run just fine this way. My caching partner has a giant coupon book for discounts at many restaurants and Streets&Trips comes in real handy for quickly locating ones that are close to where we are geocaching. I just use my old faithful yellow eTrex for finding the cache but will soon be using a GPSMap 76S that should be under the Xmas tree. Poindexter, www.geocities.com/fairbank56

Although I won't have my 76S til xmas, one of the many features that sold me on asking for this one is the external antenna jack. I do a lot of hiking and like to overlay my track on topo maps after the hike. I plan to buy one of the very small external antenna's and mount it on a short lightweight pole attached to my backpack. That way I don't have to hold the gps out in the clear all the time. They don't work very well stuffed in a pocket. This will also allow use of the external antenna while using the gps in a car. Just another thought, Poindexter, www.geocities.com/fairbank56

You don't need to spend much money at all to do this. You can download USGS topo maps for free or minimal cost, join them together and crop the area you want, download your tracks and print them out. I do this all the time and have never "had" to purchase any commercial sofware to do it although I have purchased several programs because I like playing around with this stuff. See my web page for details. Poindexter, www.geocities.com/fairbank56

I assume you are talking about 1:24000 scale topo maps as these have the most detail. No, you cannot upload these to a GPS. And if your talking about a handheld unit, what would be the point? At 1:24000 scale, you'd have about 1km x 1.3km on a "big screen" like the GPSMap 76 (1.6"x 2.2" screen), and with a screen resolution of 180 x 240 trying to show a vector map, it wouldn't look very sharp like a paper topo map. And what happens if your GPS dies? You can print your own quality topo's for the cost of the paper and ink with all your waypoints, tracks, and whatever else you want. Not trying to flame you here, but I just don't see the point of trying to put a large scale detailed map on a tiny low res screen. As for which unit to buy, I'm looking to upgrade from my old faithful yellow eTrex to the GPSMap 76S (garmin). It's a large handheld, WAAS, external antenna jack, 24M memory, altimeter, compass, audible alarms, it's waterproof (even floats), and has quadrifilar internal antenna...everything I want in a handheld unit. Can't wait til Xmas! Poindexter www.geocities.com/fairbank56

Check out Randy Steele's site at www.nb.net/~resteele/newsites/3dtopos.htm Also try www.visualizationsoftware.com/3dem.html If your already using Oziexplorer, they have an add-on program called 3D Oziexplorer for $25 that will do this for you. The problem with some of the commercial software such as Delorme's Topo USA is that they just don't have the detail and resolution of the USGS 1:24000 DRG topo's of which many are freely available. Poindexter, www.geocities.com/fairbank56

Yes you can. Just click on File>Print>Print Map Image. In the print map window, on the left, select either "selected-fit to page(s)" or "selected-to scale". Then click on the button on the left and a "select printing area" window will pop up. Put the mouse pointer at the upper left area of the map you want to crop and then double click and drag to select the area you want. The only problem is that it doesn't give you any indication of the size of the area you have selected in pixels. What I do with USGS DRG topo maps is crop the map image to the size I want before importing it into Ozi, then import it and auto cal and then just print to scale. I have a help page for more info on doing this at www.geocities.com/fairbank56 Poindexter

Trailblazer #1 Technically speaking, latitude/longitude is neither a grid or a rectangular system. It is an angular coordinate system and the lines of latitude and longitude are called graticules. Magellan315 You are confusing accuracy with resolution. The coordinates with the greatest resolution is #4 deg.ddddd which gives a resolution of 3.6 feet. Poindexter, www.geocities.com/fairbank56

Iv'e just started playing around with ExpertGPS and have found a consistant error in the calibration of the online topo maps. I have checked several different quads from the central Maryland area and have found that the northing UTM grid lines are shifted about 10 meters to the south. Gartrip and Oziexplorer are "right on the money". The resolution of the maps downloaded thru ExpertGPS is about 250 pixels per kilometer on the map while USGS DRG's are mostly 410 pixels per kilometer and the Teale DRG's are even higher. I'll have to try the beta version of ExpertGPS that allows you to use your own scanned maps. Poindexter, www.geocities.com/fairbank56

USGS 7.5 minute topo maps conform to United States National Map Accuracy Standards which specity that for horizontal accuracy not more than 10 percent of the points tested shall be in error by more than 14 meters (about 50'). To get the most accurate UTM coordinate for a point on these maps, you should download your quad as a geotiff file, then download a free program called ER Viewer from www.ermapper.com/download_new/ and open the quad in this program. It uses the geo-referencing tags that are imbedded in these geotiff files to give accurate coordinates for the position you have selected under the cross-hairs. See my help page for more info. Poindexter, http://www.geocities.com/fairbank56

For the best map resolution for the best printout, I download the DRG's (USGS Quads) that I need, join them if necessary, crop them and then import them into Oziexplorer for automatic calibration. You can put all the waypoints and tracks you want as well as the UTM grid on the maps before printing. Expertgps is nice but the maps are made up of lots of little .jpg files so they do not have nearly the resolution of the DRG's which are in .tif format. See my help page for more info. Poindexter, http://www.geocities.com/fairbank56

I have a help page on this subject that you may find useful. Poindexter http://www.geocities.com/fairbank56