Jump to content

Garmin eTrex measure distance accuracy


nemethmik

Recommended Posts

Have you noticed that when measuring distance with your eTrex in the range of 1.0 - 9.9 miles it shows only two digits? Which is quite bad accuracy (ca 500 feet). A couple of multicache gives the location of the final cache as a bearing degree (e.g. 45) and distance (e.g. 1.25 miles); you cannot find these caches with an eTrex. On the other hand, a Garmin GPS Map 76 shows three digits (1.00 - 9.99), which is way much better accuracy. Why do you think Garmin has introduced this discrepancy?

 

BTW, I upgraded my eTrex with the latest firware but, despite its promises, it helped nothing.

Link to comment

Now I don't use miles, normally, but kilometers, and they do show as 1.00 to 9.99 km, until you hit 10.0 km. It starts with 0.00 m, until 9.99 meters. Then it's with one decimal until 99.9 meters, then integer meters until 999, then 1.00 km, which means a 10 meter resolution. At the other end, after 999 km it will change to four digits, allowing a distance of up to 9999 km.

 

Mine is an eTrex Vista. Is the yellow different, or what model are you using?

 

Anders

Link to comment

If you have a bearing and a distance, project a waypoint to the new location, then just do a GOTO like you did to get to the first location. Then when you get less than a tenth of a mile from there it will read in feet.

 

Projecting a waypoint is easy, but if you're not familiar with it, do a seach here for it. It's been discussed quite a bit.

 

Me and that dog are gonna take a walk in the woods, and only one of us is coming back...

Link to comment

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 icon_wink.gif) 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.

Link to comment

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 icon_wink.gif) 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.

Link to comment

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

Link to comment

I have an eTrex Legend.

I changed to the metric system and I still have only one digit after the decimal point. It does not matter what is the unit systems, or the distance range: my Legend has only one decimal precision icon_frown.gif

However, (thanks brdad!) when entering distance on the Project Waypoint screen I have two decimal digits icon_smile.gif

Thanks a lot for the help to all of you!

 

[This message was edited by nemethmik on August 21, 2002 at 02:57 PM.]

Link to comment

I have an eTrex Legend.

I changed to the metric system and I still have only one digit after the decimal point. It does not matter what is the unit systems, or the distance range: my Legend has only one decimal precision icon_frown.gif

However, (thanks brdad!) when entering distance on the Project Waypoint screen I have two decimal digits icon_smile.gif

Thanks a lot for the help to all of you!

 

[This message was edited by nemethmik on August 21, 2002 at 02:57 PM.]

Link to comment

quote:
Originally posted by Anders:

Which firmware version are you using?


2.39 (eTrex Legend)

quote:

Besides, if you measure a distance on the map, and find the figure is varying, it's probably because you are measuring from your current position, and that varies all the time, even if you don't move, due to measurement inaccuracies.


It's OK. Thanks.

Link to comment

If I select a waypoint, that's 0.88 km away, on my Vista, and then ask it to GoTo that point, the navigation page says it's 878 meters away.

 

If I select the second closest, which in this case is 6.33 km away, the navigation page says - you guessed it? - 6.33 km away.

 

I really can't understand why the Legend should be different? Do you have a deep scratch in the display window right there? icon_biggrin.gif

 

Anders

Link to comment

If I select a waypoint, that's 0.88 km away, on my Vista, and then ask it to GoTo that point, the navigation page says it's 878 meters away.

 

If I select the second closest, which in this case is 6.33 km away, the navigation page says - you guessed it? - 6.33 km away.

 

I really can't understand why the Legend should be different? Do you have a deep scratch in the display window right there? icon_biggrin.gif

 

Anders

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...