Poindexter

Mapopolis is an excellent mapping program for your pda. I use it on a pocket pc with windows 2003se but they have a version for palm as well. There's a utility to convert the .gpx files to mapopolis maplet so you can see all the caches on the maps.

I think you have one of the "new" yellow etrex models that have WAAS capability. There has been very little public information about this other than from the people like you who have asked about this version 3 firmware. It would be nice to hear from Garmin on this. Others have said that they have a yellow eTrex with version 3 firmware and WAAS can be enabled via the setup menu.

Is this correct or were there other handheld receivers before? What about the GPS 45? Cornix I think Magellans Nav 1000 was one of, if not THE, first handheld back in 1988. You could get one for around $2500.00

10 months! Found my first cache on 3/17/01 when there were only 2 caches in Maryland. Didn't check back in til January of 02 and then there were plenty of caches to go look for.

In Oziexplorer you store waypoints in files with a .wpt extension. In both the PC version and the PPC version you load whatever waypoint files you want after loading the map. GSAK will export directly to Ozi waypoint files.

If your really considering a new GPSr then also consider Pocket PC's I use one with a bluetooth GPS receiver and download the topo's I need for free. I currently use Oziexplorer to work with the topo's and GPSr. While the garmin topo's are "ok" they just didn't provide the detail I was looking for. Here's how it looks on the Dell Axim x50v

We understand that it is a datum problem but in this case it's not an end user error. We are using programs that autocalibrate these maps using the supplied geo-referencing data however that data was incorrect in this case so we must correct it manually. For those that are using these programs in the future with these geotiff files I would suggest that after the autocal is done that you immediately check for error by placing your cursor over the utm tic marks on the maps and make sure the coordinates are correct.

Years away...Look at the left two columns in this chart from the USCG Navigation Center GPS modernization page.

In general, yes. 24 active satellites gives very good coverage but that can't overcome you being down in a valley, among buildings or under heavy tree cover. In these situations the signals you are receiving are coming from sat's that are either relatively close to each other or in the same general direction from you and that's when accuracy suffers. For websites, try Quest and Sam Wormley's pages. The Usenet group sci.geo.satellite-nav is also a good resource. The resolution of the codes is determined by the number of elements in the code. The L1 C/A has 1,023 whereas the L5 will have 10,023 This is determined by different clock rates.

No

Semantics Never heard it called "receiver geometry" but we are talking the same thing here. A google search on "gps" and "receiver geometry" gives 219 results. Change that to "satellite geometry" and we get 8,060. Satellite geometry refers to the positions of the satellites in relation to the receiver. A receiver's accuracy is affected by satellite geometry. The satellite geometry that provide the highest accuracy is when one satellite is directly overhead while the others are evenly spread around the horizon. A poor geometry is when the satellites are close together because they do not offer distinct positions for triangulation. Makes no sense. The satellites are in orbit (i.e. in motion) so the satellite geometry is constantly changing. Professionals in the field use software to determine the time of day when the best geometry for a given location will be so that they will get the most accurate coordinates when they are trying to be as precise as possible. Huh? We don't even receive the L2 on our receiver's. We receive the C/A code on the L1 frequency which currently gives us 10 to 20 meters. Ionospheric delay causes an average error of about 4 to 5 meters. The 100 meter error we use to get before May of 2000 was due to intentional dithering of the L1 C/A signal by the Dept. of Defense. The L5 code will have 10 times the resolution as the L1 C/A code length.

Not unless yours can receive both L1 and L2 signals. The ability to receive two different frequencies is what allows reduction of ionospheric errors which is the cause of the most error next to satellite geometry. It does seem that the military uses a lot of "civilian" receivers. Iv'e even seen them on Navy ships.

The military receivers use an encrypted code transmitted on both the L1 and L2 frequencies. This allows them to quickly dither or turn off the "civilian" signals.

The single most significant factor affecting accuracy is satellite geometry. Boosting signal strength will get us better coverage under tree cover and therefore better satellite geometry. That means better accuracy under the right conditions. There are no block III satellites. The new satellites to be launched this year are block IIR-M sat's. They will have a new signal added (L2C on the L2 frequency) which will give an accuracy of 5 to 10 meters for those receivers that can receive the L1 and L2 freq's. The fourth generation of satellites (block IIF) are scheduled for launch beginning in 2006. These will include the new L5 signal and provide accuracies of 1 to 5 meters for the multi-freq receivers.

Iv'e been using the i Trek bluetooth receiver which is available for $126.00 which includes a second battery free but you'll probably never need it as it will run for over 20 hours. It works great with Oziexplorer, Streets and Trips and Mapopolis. Don't know about Delorme.

I think it's way too early to be concerned about this. For one thing, even if all the new sat's were in place and fully operational today, our current receivers would not get the accuracy of 1.5' that you quote. Our receivers need the L2 and the new L5 frequencies to improve accuracy to 1 to 5 meters. We might see a slight accuracy improvement due to stronger signal strength and therefore better satellite geometry under tree cover. You'll still need differential corrections to get from 1/2 to 5 meters accuracy and survey grade instruments to get to that 1.5' radius. Multi-freq receivers will be expensive and battery hogs. Let's see how things are in about 2 years. Probably not much different than today as far as geocaching goes.

I tried that. The georeferencing data is not in plain text. There is a reference to WGS84 at the very bottom of the file and I changed it to NAD27 but it had no effect when importing to Oziexplorer, I still had to manually change the datum. The tif file is read-only so you'll have to remove that attribute before making any changes to the file. I also downloaded the files from GISDataDepot as I have an account there. The tif file from there has no georeferencing data in it so you must use the world file (tfw) that comes with it and it is screwed up as well. Weird

The problem is with the georeferencing information within the tif file. Also, the associated tfw file is incorrect as well. When I import the tif file into Oziexplorer (not using the tfw file) it auto-calibrates it using WGS84 datum. This gives incorrect coordinates because the map datum is NAD27. In Ozi, I use the "check calibration" feature and change the datum to NAD27 and "save" and then all is OK. If I import and auto-calibrate using the tfw file I can see that the calibration points are in the wrong place. The longitude is correct, but latitude is way off. First time Iv'e run into this problem.

Give us the three coordinates you have, the location of the intersection and the quad name.

Weather has so little effect on signal strength that the end user would not see any difference. This is another common myth plastered all over the web. Rain, snow, clouds and GPS reception.

Iv'e updated my webpage for getting free USGS Digital topo maps to a simple clickable map of the U.S.

I have one on my profile page. You should also be able to do it on your cache page. They are freely available on the Internet. It is interesting to see how often your pages are looked at. Just added one to my cache page, works fine. Thanks for the idea

Not true. Either the book is wrong or you have misinterpreted it. Receivers with built in "magnetic" compasses are quite accurate and you do not have to be moving at all. Even ones that do not have magnetic compasses do not require you to be moving at that speed for the heading to be accurate. A steady walking speed of 2 to 3 mph is sufficient as long as you have good satellite coverage. Declination (variation) is the difference between True North and Magnetic North. They are different because the magnetic north pole is in a different location than the True north pole. Local variations caused by ferrous material is called deviation.

Roger that Greymane, that's too bad, these are the most compact converters Iv'e seen yet.

I don't know what the conversion to US dollars is or what their shipping costs are but try here.