Problem Finding Cache

[Gill Fisher]

I went on my first cache hunt with my Son and Grandson recently and ran into an unexpected problem. We were hunting the cache at the Chester SC state park and I entered the coordinates into my Garmin Etrx using the UTM system and off we went. But my GPS was off by 1000 to 1500 feet. We finally reverted to an app on my Son's phone and got close. Then we looked at a picture that someone else posted online and found the cache. But I was very disappointed that I couldn't get closer with the GPS. It has always been very accurate on hikes. I triple checked the coordinates I had entered and they were correct. Any suggests as to what may have gone wrong. Thanks

 

GF

[+Cardinal Red]

I went on my first cache hunt with my Son and Grandson recently and ran into an unexpected problem. We were hunting the cache at the Chester SC state park and I entered the coordinates into my Garmin Etrx using the UTM system and off we went. But my GPS was off by 1000 to 1500 feet. We finally reverted to an app on my Son's phone and got close. Then we looked at a picture that someone else posted online and found the cache. But I was very disappointed that I couldn't get closer with the GPS. It has always been very accurate on hikes. I triple checked the coordinates I had entered and they were correct. Any suggests as to what may have gone wrong. Thanks

 

GF

 

I would suggest that you don't yet fully understand coordinate systems. How then is "triple checking" going to yield the correct result? Why did you find it necessary to use the UTM coordinate system? Have you successfully entered UTM coordinates to the GPS previously? Where did you get the coordinates that you entered? Which cache were you looking for? EXACTLY what did you enter into the GPS? Which Datum did you use? You are sure you had the GPS set to accept UTM? Did you look at the coordinate display on the GPS during the search? Did the coordinates display still look the same as what you had originally entered?

 

With all those unknowns it would be next to impossible for anyone reading a Forum to simply figure out exactly what the problem was - without quite a bit more specific feedback from you. If you can tell us exactly what you did, we can figure it out.

[Gill Fisher]

I prefer to use the UTM system because I have often determined a location from a topo map using a UTM grid tool. The Etrex is set so that the position format is UTM UPS. The map datum is NAD27 CONUS. I went to the Find A Geocache tab on this website, went to Lakes Region Challenge - Chester State Park, found the UTM coordinates there and entered them into my GPS. I triple checked by comparing the coordinates on the website several times with, what I had entered into the GPS to confirm that I had entered them correctly and without error. I had the GPS turned on and in my hand as I tried to navigate to the cache. I had the GPS on the map page and it was indicating that the cache was across the access road to the park while the description for the cache we were hunting said it was 60 feet off the trail. We had already bushwhacked probably 100 yards or 300 feet from the trail and the GPS was indicating that the cache was at least that much further and across the access road when we stopped using the GPS and started using the phone app which took us back somewhat toward the trail, and further down the trail, when we actually found the cache. At that point the GPS was actually leading us away from, rather than toward the cache.

[+Cardinal Red]

I prefer to use the UTM system because I have often determined a location from a topo map using a UTM grid tool. The Etrex is set so that the position format is UTM UPS. The map datum is NAD27 CONUS. I went to the Find A Geocache tab on this website, went to Lakes Region Challenge - Chester State Park, found the UTM coordinates there and entered them into my GPS. I triple checked by comparing the coordinates on the website several times with, what I had entered into the GPS to confirm that I had entered them correctly and without error. I had the GPS turned on and in my hand as I tried to navigate to the cache. I had the GPS on the map page and it was indicating that the cache was across the access road to the park while the description for the cache we were hunting said it was 60 feet off the trail. We had already bushwhacked probably 100 yards or 300 feet from the trail and the GPS was indicating that the cache was at least that much further and across the access road when we stopped using the GPS and started using the phone app which took us back somewhat toward the trail, and further down the trail, when we actually found the cache. At that point the GPS was actually leading us away from, rather than toward the cache.

 

OK. You prefer UTM. Fine. As long as you understand what you are doing, you can use any preference you like. You have the GPS set to UTM UPS and NAD27 CONUS. You found the UTM coordinate conversion on the Cache Page. ALL CACHE PAGE COORDINATES ARE PRESENTED IN THE WGS84 DATUM. Datum mismatch. Immediate fail right there. That mismatch can easily put you off target by 200 Meters. Sounds like that is about the error you were experiencing.

 

When you are entering coordinates obtained from a Cache Page, you need to set the Datum on the GPS to WGS84. If the Topo Maps you pull coordinates from are referenced to NAD27, then you need to have the GPS set to that. If you are pulling from both sources for the same trip, you have the GPS set correctly for each data entry (do all like Datum coords first, and then the other ones instead of doing a lot of switching back and forth). Afterward you can change to ANY FORMAT and DATUM setting available to you. At that point, the coordinates can LOOK totally wrong to your eyes, but the GPS will take you to the correct intended location if you did it right.

 

Trust me, anybody who mixes Datum Formats will eventually forget what they set the GPS to the last time it was used. Then you toss new numbers at it and go to the wrong spot. I have already figured out in the field what I had done wrong. I looked up the numbers on the GPS and wrote them down. I changed the GPS setting and then re-entered those same numbers. Then I followed the GPS to what I was looking for. Fun times. Hopefully that is the solution to your problem. Good Luck.

 

If that doesn't fix the problem, come back again with even more information. But I have a good feeling about this.

[Gill Fisher]

That is what I suspected the problem might be but I had not found what the datum for geocaching might be. Can I ask you where you found the information that geocaching uses WGS84? I looked for that information and couldn't find it. This is the first time I have run into this problem. Also, are you saying that I can enter the coordinates in WGS84 and then return the GPS to NAD27, since that's where I keep it for hiking, and still find the cache? Thanks for your help.

 

GF

[Kybelum]

That is what I suspected the problem might be but I had not found what the datum for geocaching might be. Can I ask you where you found the information that geocaching uses WGS84? I looked for that information and couldn't find iT

 

https://www.geocaching.com/about/glossary.aspx

 

WGS84

The most current geodetic datum used for GPS is the World Geodetic System of 1984 (WGS84). The significance of WGS84 comes about because GPS receivers rely on WGS84. Geocaching uses the WGS84 datum by default. We also use the coordinate format HDDD MM.MMM, which is a standard for handheld GPS receivers. HDDD means Hemisphere and degrees. MM.MMM are minutes in decimal format. It is critical that the format be correct, otherwise geocachers will be unable to find your geocache.

[+Cardinal Red]

That is what I suspected the problem might be but I had not found what the datum for geocaching might be. Can I ask you where you found the information that geocaching uses WGS84? I looked for that information and couldn't find it. This is the first time I have run into this problem. Also, are you saying that I can enter the coordinates in WGS84 and then return the GPS to NAD27, since that's where I keep it for hiking, and still find the cache? Thanks for your help.

 

GF

 

Look at the bottom of any cache page. Preferably a newly placed cache. There won't be so many logs to wade through to get to the bottom. Coordinates are in the WGS84 datum

 

Yes, after you have correctly entered your WGS84 coordinates, you can switch the GPS back to NAD27 (or any other Datum you care to). Set to NAD27, any WGS94 coordinates will be shown as the NAD27 conversion. They won't look the same as what you originally entered, but they will lead you to the same spot. If someone asks you to tell them what the WGS84 Datum coordinates are, you would have to temporarily switch back to WGS84 before reading off the coordinates to them.

[Pup Patrol]

That is what I suspected the problem might be but I had not found what the datum for geocaching might be. Can I ask you where you found the information that geocaching uses WGS84? I looked for that information and couldn't find it. This is the first time I have run into this problem. Also, are you saying that I can enter the coordinates in WGS84 and then return the GPS to NAD27, since that's where I keep it for hiking, and still find the cache? Thanks for your help.

 

GF

 

Help Center → Other → Conversions

http://support.Groundspeak.com/index.php?pg=kb.page&id=208

 

3.3. WGS-84 and HDD(D)° MM.MMM Datum and Format

 

Why do we use WGS-84 and HDD(D)° MM.MMM Datum and Format?

 

Most GPS receivers are set coming out of the box with WGS-84 and HDD(D)° MM.MMM Datum and Format. Using this setting will be less likely to confuse new GPS owners.

 

3.4. GPS Coordinates Don't Match the Map

 

My GPS coordinates don't match the location on the map. What's wrong?

 

The coordinates are most likely in the wrong format or datum. Make sure your GPSR uses WGS-84. If you need more help, please see the Related Page below.

 

Note that there is a slight variation in the Topozone maps when linked from geocaching.com: the Topozone website uses NAD-27, a different coordinate datum.

 

Another possibility is that the GPS may be set to "Lock to Roads." If this is the case, even when you're in the middle of the forest, the GPS will state that you're in the middle of the nearest highway. Be sure to turn off this feature if you have it.

 

B.