Jump to content

DarrenF

+Charter Members
  • Posts

    63
  • Joined

  • Last visited

    Never

Everything posted by DarrenF

  1. quote:Originally posted by Alphawolf:I guess you mean an_*implied*_resolution of 0.1 ft., right? If you get a real resulution of better than 30 ft. your doing great! Very well, I should have said it displays the distance to a precision of 0.1ft. In fact, in maximum zoom (20ft) moving the pointer 1 pixel equates to about 0.6ft, and the displayed distance seems to change only in increments of about 2.1ft (and it is erratic, going up AND SOMETIMES DOWN as you move the pointer away from the center of the display). Of course, this is all about theoretical/mathematical precision, completely seperate from the estimated positional accuracy of the GPS's fix (resolution != EPE). In addition, AFAIK, the GPS stores positions with a precision of .00001 deg (the other display modes, mm.mmm and mm ss.s, are somewhat less precise) which is about 3.6ft (for .00001deg latitude, a bit less for longitude away from the equator). df
  2. I just realized that (on an eTrex Legend, and likely Vista too) using the map in pan mode may be a better (i.e. more precise, albeit more work) method of 'projecting' a nearby (<0.1mi away) waypoint than using the Project Waypoint function. It will allow be to create a waypoint at any bearing [even in mils ) and at any distances with a resolution of 0.1ft up to 527.9ft [0.1mi resolution thereater, up to 999.9mi, and intiger miles over 1000mi) Obviously things will be a little different in metric mode.
  3. I just realized that (on an eTrex Legend, and likely Vista too) using the map in pan mode may be a better (i.e. more precise, albeit more work) method of 'projecting' a nearby (<0.1mi away) waypoint than using the Project Waypoint function. It will allow be to create a waypoint at any bearing [even in mils ) and at any distances with a resolution of 0.1ft up to 527.9ft (0.1mi resolution thereater, up to 999.9mi, and intiger miles over 1000mi) Obviously things will be a little different in metric mode.
  4. ...this program should come with a warning label. I lost some sleep last night because I couldn't drag myself away from it df
  5. ...this program should come with a warning label. I lost some sleep last night because I couldn't drag myself away from it df
  6. quote:Originally posted by Anders:-17 feet is rather "normal". I've seen more than -100 feet on my unit. Besides, GPS altitude is above the geoide, which isn't exactly the same as Mean Sea Level. Anders I thought modern Garmins used tables and interpolation to adjust the elevation relative to the geoide to altitude relative to (approximate local) sea level? I've also 'heard' (for what it's worth) that the accuracy for altitude is 'typically' about 1.5 the accuracy for horizontal position; so if you're getting an EPE of ~20ft, you can expect an elevation accuracy of ~30ft (±). Has anyone else heard this rule-of-thumb? df
  7. quote:Originally posted by Anders:This isn't true. If you set the GPS to mils as the unit for bearings, you can set any of 6400 directions. One mile away, these points are 2.6 feet apart. Or 0.79 meters. One kilometer away, they are .49 meters apart. Since the resolution along the radii (do you say so in English?) is 10 meters, you have to be 20372 meters away to have the same resolution in both directions. Anders Excellent observation. This is why I keep returning to these forums I learn something new every day. However, I calculate the points to be about 5.1ft ( 1.58m) apart at 1 mile (1.61km) distant; and .98m apart at 1km distant. I used arclength=r*theta, and calculated that 1mil * 2*Pi radians/6400mils = .000982 radians. I realize the arclength isn't the shortest distance between the two points, but it should be pretty close, especially as the radius increases. So in summary, the best resolution for projecting a way point is obtained by setting the bearing to mils (Setup Menu|Heading|Display) and the distance to metric (Setup Menu|Units|Distanct/Speed). PS-radii is perfectly correct in English; I never would have guessed English isn't your first language. df
  8. quote:Originally posted by Anders:This isn't true. If you set the GPS to mils as the unit for bearings, you can set any of 6400 directions. One mile away, these points are 2.6 feet apart. Or 0.79 meters. One kilometer away, they are .49 meters apart. Since the resolution along the radii (do you say so in English?) is 10 meters, you have to be 20372 meters away to have the same resolution in both directions. Anders Excellent observation. This is why I keep returning to these forums I learn something new every day. However, I calculate the points to be about 5.1ft ( 1.58m) apart at 1 mile (1.61km) distant; and .98m apart at 1km distant. I used arclength=r*theta, and calculated that 1mil * 2*Pi radians/6400mils = .000982 radians. I realize the arclength isn't the shortest distance between the two points, but it should be pretty close, especially as the radius increases. So in summary, the best resolution for projecting a way point is obtained by setting the bearing to mils (Setup Menu|Heading|Display) and the distance to metric (Setup Menu|Units|Distanct/Speed). PS-radii is perfectly correct in English; I never would have guessed English isn't your first language. df
  9. That is very cool. I wish there were something eqivalent for the MapQuest arial photos... df
  10. quote:Originally posted by Alan2:The problem is people throw out the word Mapsourse which is the name of a "brand name" of Garmin map programs without mentioning the "model". As Peter mentioned these include Mapsourse Metroguide, Mapsource City Select, Mapsource City Navigator that have routing data, Mapsourse Topo and Mapsource Roads and Recreation that don't, etc. It's like saying my Garmin does this, why doesn't it do that? and not mentioning your Garmin Vista or your Garmin Legend. And on top of that, to add to the confusion even more, they call their PC mapping and GPS interface software simply "MapSource". That's the "MapSource" I was referring to in my post. df
  11. quote:Originally posted by Alan2:No external antenna hookup for the Vista. No *hookup*, but using an external (re-radiating) antenna with the eTrex models is possible: http://safetracgps.com/reraidiating.htm [i have no affiliation with that company, nor do I know anything about them, I simply found the link with Google] df
  12. Converting a bearing & distance to a latitude & longitude offset is fairly straightforward: latitude offset (in decimal minutes) = distance (in nautical miles) * cos(bearing) longitude offset (in decimal minutes) = distance (in nm) * sin(-bearing) / cos(latitude) note: 1 nm = 6076ft The above assumes you are near sea level, the earth is a sphere, and probably break down near the poles... and should be checked by someone not doing math by the seat of his pants before being used df
  13. Converting a bearing & distance to a latitude & longitude offset is fairly straightforward: latitude offset (in decimal minutes) = distance (in nautical miles) * cos(bearing) longitude offset (in decimal minutes) = distance (in nm) * sin(-bearing) / cos(latitude) note: 1 nm = 6076ft The above assumes you are near sea level, the earth is a sphere, and probably break down near the poles... and should be checked by someone not doing math by the seat of his pants before being used df
  14. The eTrex Legend (and I presume Vista) can project waypoints. But there are of course some limits as to the precision which a projected waypoint can be placed. If the units are set to miles, the distance is entered to the nearest .01 mile (about 53ft), if the units are set to metric, the distance is entered to the nearest .01 km (about 33ft). The bearing must be entered in integer degrees (I haven't played with it much, but I think this is the only input format for the bearing, no matter what the settings). So projected waypoints can be placed any of the 360 equidistant points points on a circle any multiple of 52.8ft (10m, if using metric) from a given waypoint, clearly the further away from the waypoint, the further apart these possible point become--e.g. at 1 mile away, they are about 92 feet apart. df
  15. There is a build of G7toWin for WindowsCE/PocketPC devices called G7toCE here http://home.attbi.com/~g7towin/#g7toCE I have a WinCE2.11 device (Casio E-100) but I haven't tried connecting my GPS to it, yet df
  16. There is a build of G7toWin for WindowsCE/PocketPC devices called G7toCE here http://home.attbi.com/~g7towin/#g7toCE I have a WinCE2.11 device (Casio E-100) but I haven't tried connecting my GPS to it, yet df
  17. Sounds like you are finally getting nearer to understanding this elusive bug. Coincidentally, I filled up my track-log (it maxes out at 99%, not 100%, apparently) on purpose last night. But I didn't cycle the power or turn GPS on/off. Anyhow, my timezone setting is still firmly and correctly set on US - Eastern. Does it make a difference if "Wrap When Full" is selected? Perhaps some sort of overrun problem, where the track data is overwriting the settings data in memory. Purely speculation. I wonder if ANY full track log would cause the problem, or it there's something 'special' about your particular track log that causes the problem. It's times like this that a ARM CPU emulator running the firmware code would be fun to play with. df [This message was edited by DarrenF on August 20, 2002 at 08:03 AM.]
  18. Sounds like you are finally getting nearer to understanding this elusive bug. Coincidentally, I filled up my track-log (it maxes out at 99%, not 100%, apparently) on purpose last night. But I didn't cycle the power or turn GPS on/off. Anyhow, my timezone setting is still firmly and correctly set on US - Eastern. Does it make a difference if "Wrap When Full" is selected? Perhaps some sort of overrun problem, where the track data is overwriting the settings data in memory. Purely speculation. I wonder if ANY full track log would cause the problem, or it there's something 'special' about your particular track log that causes the problem. It's times like this that a ARM CPU emulator running the firmware code would be fun to play with. df [This message was edited by DarrenF on August 20, 2002 at 08:03 AM.]
  19. OK, perhaps the calculator isn't incorrect with respect to 0^0. It's apparently a still-debated mathematical topic, see http://mathforum.org/dr.math/faq/faq.0.to.0.power.html My HP48GX agrees with your HP48SX and the Microsoft Windows Calculator (v4.0) in giving 1. However, MS Excel returns an error. I don't have Maple or Mathematica handy to see how they weigh in. In any case, there is an argument to be made for either answer; 1 or undefined/error. df
  20. According to the MapSource change log: "Changes between version 4.00 and 4.03 include the following:" ... "Added ability to remove route calculation data from maps to yield a smaller total data size." I'm using MapSource v4.09, and I do find an option to remove route calculation data, BUT it doesn't seem to make any difference. When I select maps with it on or off, it lists the same size I would really like to take advantage of this feature to help maximize use of the 8MB in my Legend, but I can't figure out how to make it work. df
  21. According to the MapSource change log: "Changes between version 4.00 and 4.03 include the following:" ... "Added ability to remove route calculation data from maps to yield a smaller total data size." I'm using MapSource v4.09, and I do find an option to remove route calculation data, BUT it doesn't seem to make any difference. When I select maps with it on or off, it lists the same size I would really like to take advantage of this feature to help maximize use of the 8MB in my Legend, but I can't figure out how to make it work. df
  22. I've been using v2.40c on my Legend for over a week now, and I haven't had that problem, that I know of. df
  23. For what it's worth, I've seen "accuracy" (I assume they use this term on the newer eTrexi rather than "EPE") readings as low as 7ft (standing still a while in an open field with WAAS) on my eTrex Legend. A friend of mine (who owns an eTrex Vista) says he's seen it as low as 5ft. df
  24. quote:Originally posted by Krenath:Just discovered that my Venture displays this screen. Is there any documentation for the "out-in-out" keypresses? And are there any more such hidden screens? The only other one that I'm aware of is the one that comes up with you power on while depressing the click stick. WARNING! Some people have indicated that using this diagnostic mode while able to lock onto a satellite could mal-adjust some internal calibrations. Read more here: http://celia.mehaffey.com/dale/secret.htm I'm most interested in the "Stack" portion of that "out-in-out" diagnostic screen. I'd like to figure out what some of the values mean, I'm hoping it's possible to determine the map memory free/used from there (since there doesn't seem to be any other way to do it). I'm also curious about the Shutdown Error Reports. Selecting one and pressing the click-stick doesn't seem to do anything, but I wonder if it is sending anydata via the serial port about the date/time/etc of the shutdown (otherwise this 'diagnostic report' is of questionable value) df
  25. My GPS, upon power-up, first displays the Garmin copyright info ("eTrex Legend Copyright 1999-2002") then the "©AND Ireland Ltd."... This is a reference to the Ireland division of AND International Publishers (http://www.and.com), which in whole is based in the Netherlands. df
×
×
  • Create New...