MAP 76 Field Trials - Day 3 and Final

[Guest Growley]

Today I was back in the woods on a new jogging trail that had denser canopy cover and was very "hilly" compared to my "flat" jogging trail that I tested on the other day. Here is what I ended up with. Once again I never lost a signal. The GPS dropped to 2 birds once but averaged between 4 and 6. HOWEVER.... I walked about a half mile and marked 4 waypoints. I then turned around and selected GOTO the first waypoint, which got me within 50 feet. I had the screen zoomed into 50ft as well. It was down hill from there. The rest of the way out left a track that, on the screen, appeared to be a totally different trail, yet I was on the same trail I walked in on!! Got to my car and was 60.9 feet from the waypoint. On the screen my tracks were as much as a 1/2 inch apart zoomed into 50ft. Now if this is normal, I guess I'll live with it however, I feel it is totally unexeptable. Were it not for the many features of the MAP 76 it would have already been taken back. AND depending on the responses/your input it may go back tomorrow. Maybe map and compass is the way to go.

[Guest napgravy]

I just purchased a GPSMAP 76 also. This (long) weekend I plan on doing some comparisons with my old Magellan 315. I know the 315 is pretty good at holding a lock under tree cover but I haven't been out with the GPSMAP 76 yet.

 

Its been good to read your impressions of the unit and I plan on posting my own once I get a feel for it.

[Guest mcb]

I think your expectations may be just a little harsh. Sure if you had walked that trail out and back and it was out in the open and had you had 9 satellites and WAAS correction going then you might have a case. But as you said you where in heavy tree cover and at times you only had 2 satellite in view. My guess is that you didn't have a WAAS differential correction going either. Given that, I would say your GPS was doing pretty good if it had you within 50 ft of the outgoing path on the return path. Try the same test out in the open and I bet you will get results more like you expected. Be thankfull that the GPSMAP 76 maintained lock as well as it did. If it was and eTrex you would probable have lost lock several times. I think you GPS is working just fine.

 

mcb

[Guest Khao Mun Gai]

I have had the GPSMAP 76 for about 3 weeks. I love it and love all of its features.

 

I have experienced similar "drift" to what you are describing a number of times and have simply accepted it as par for the course. There have been times where it has brought me to within 5 feet of a previously marked waypoint and others where I have been off by 50 feet. I think that it has more to do with the satellites that are in use each time, perhaps, than the unit itself. I wonder if you had another unit along for precisely the same MARK and returns if it would have similar problems?

[Guest gstrong1]

I also get this "drift" from my MAP76.I also get it from my Vista(when I can maintain a satellite lock).The only unit I have not gotten this with is the III Plus.I'm sure it is the antenna design.I've gone out many times with all 3 units & marked waypoints & tracks. The III Plus is pretty much right there all the time.As I've said in other posts, from my experiences, the MAP76 seems to have to settle in to its position.I'll walk a path & stop & mark a point on all 3 units.Then continue on for a while & mark a few more points.When I turn around & head back, when I get to the nearest point on the III Plus,I'll stop.The MAP76 will be off by as much as 40 ft., depending on the overhead tree cover.If I stand there for up to 5 minutes, the MAP will settle in to the correct numbers & usually be within a few feet.I've experienced this on cache hunts often. I'll go by the numbers on the III Plus & get to the cache, then check the numbers on the MAP.On 1 particular cache(a lot of tree cover)the III Plus had me at 5 ft. at the cache while the MAP had me at 60 ft. from the cache.I set down the units, signed the log & took my pic with the camera & buttoned the cache back up.About 5-7 minutes.When I picked the units back up, the MAP had me at 10 ft.Adding the Garmin external antenna to the MAP did not do a lot to remedy this, though it did make a slight difference.But I have to believe that the superior antenna on the III plus is the sole reason it is so responsive & repeats so well.Even out in an open field, the MAP seems to need time to settle in.I think it would be a great idea for a few cachers from the same basic locale, who own different GPS units,got together & went out to make comparisons & see if they get any results similar to mine.I'm not crazy about the "drifting",but I've come to expect it & live with it.I just don't head out on a cache adventure without the III Plus.It doesn't have the memory capacity that the MAP & the Vista have, but I've usually got them along if I need to look at a map that covers an area that needs more than 1.44 mb.Doesn't happen to often, obviously.

 

------------------

Gary "Gimpy" Strong

Rochester,NY

[Guest Geoffrey]

The GPS MAP 76 uses an external antenna with the MCX connector.Buy this adaptor: http://www.gpscity.com/accessories/antennas/mcxbnc_cable.html

Take the antenna off of the 3plus and use this adaptor on your map 76.

your map 76 internal antenna was designed only for the open road and on a boat out in the open water.

 

Geoff from Detroit

 

[This message has been edited by Geoffrey (edited 04 August 2001).]

[Guest gstrong1]

Excellent Geoffrey.Thanks.Mine's on order.I'll come back with results. .

 

------------------

Gary "Gimpy" Strong

Rochester,NY

[Guest gstrong1]

Excellent Geoffrey.Thanks.Mine's on order.I'll come back with results. .

 

------------------

Gary "Gimpy" Strong

Rochester,NY

[Guest napgravy]

Well, I did a bit of testing in a local park today. I had my new Garmin GPSMAP 76 (2.04 firmware) and my trusty Magellan GPS315 (3.14 firmware.) Here is what I found...

 

When under tree cover, the GPS315 showed a few more satellites in lock (about 2 more on average) with a stronger signal than the GPSMAP 76 did - I expected to see that. Neither unit lost a lock completely. At one point, the 315 showed 10 satellites at full signal strength. The GPSMAP 76 showed 8 locked and only 3 of those at full strength - the rest at about 1/4 or 1/2 strength. I do realize this is somewhat subjective and highly dependant on conditions. I wondered how much part the graphic user interface plays in my opinion - ie. the 315 has taller signal bars on its display so the signal must be better! Well, the mosquitos were starting to enjoy my testing a little too much so I moved out of the tree cover back to the main pathways.

 

For my next test, I found a nice tree for a landmark just off the main path. I created a MOB waypoint on both units and walked off about 120m down the path. I'd then turn around and walk back towards the tree. I did this test twice. Once back at the tree, I've give both units about 2 minutes to settle in their readings. The 315 was showing a distance to MOB of 4-6m while the GPSMAP 76 was showing a distance to MOB of 15-17m. I can't get a WAAS lock with the GPSMAP 76 in the park so that never came into play. I was hoping to see the GPSMAP 76 getting results a little closer to the MOB like on the 315. Yes, I realize this is a highly subjective and condition dependant.

 

Other impressions... I liked the GPSMAP when poking along slowly in the bush. The auto-averaging on the 315 is somewhat of a pain when you're moving along slowly. The interface and features on the GPSMAP 76 are also quite impressive. The 315 is smaller. The GPSMAP has maps but I live in Canada so the maps are quite outdated and kinda suck. No maps at all on the 315 obviously.

 

Back when I bought my Magellan, I was using firmware 1.03 with it. Somewhere in the 2.x series of firmware, it seemed to become better able to find and hold a satellite lock. Once again, this could all be my perception and/or related to the user interface. Perhaps Garmin can/will improve the GPSMAP 76 in future firmware releases. Hard to say...

 

I'm still debating whether to keep the GPSMAP 76. If I do keep it, I'll then have to decide whether or not to keep the Magellan or sell it. Had anybody else here moved from a Magellan receiver to a Garmin unit? Comments?

[Guest napgravy]

Well, I did a bit of testing in a local park today. I had my new Garmin GPSMAP 76 (2.04 firmware) and my trusty Magellan GPS315 (3.14 firmware.) Here is what I found...

 

When under tree cover, the GPS315 showed a few more satellites in lock (about 2 more on average) with a stronger signal than the GPSMAP 76 did - I expected to see that. Neither unit lost a lock completely. At one point, the 315 showed 10 satellites at full signal strength. The GPSMAP 76 showed 8 locked and only 3 of those at full strength - the rest at about 1/4 or 1/2 strength. I do realize this is somewhat subjective and highly dependant on conditions. I wondered how much part the graphic user interface plays in my opinion - ie. the 315 has taller signal bars on its display so the signal must be better! Well, the mosquitos were starting to enjoy my testing a little too much so I moved out of the tree cover back to the main pathways.

 

For my next test, I found a nice tree for a landmark just off the main path. I created a MOB waypoint on both units and walked off about 120m down the path. I'd then turn around and walk back towards the tree. I did this test twice. Once back at the tree, I've give both units about 2 minutes to settle in their readings. The 315 was showing a distance to MOB of 4-6m while the GPSMAP 76 was showing a distance to MOB of 15-17m. I can't get a WAAS lock with the GPSMAP 76 in the park so that never came into play. I was hoping to see the GPSMAP 76 getting results a little closer to the MOB like on the 315. Yes, I realize this is a highly subjective and condition dependant.

 

Other impressions... I liked the GPSMAP when poking along slowly in the bush. The auto-averaging on the 315 is somewhat of a pain when you're moving along slowly. The interface and features on the GPSMAP 76 are also quite impressive. The 315 is smaller. The GPSMAP has maps but I live in Canada so the maps are quite outdated and kinda suck. No maps at all on the 315 obviously.

 

Back when I bought my Magellan, I was using firmware 1.03 with it. Somewhere in the 2.x series of firmware, it seemed to become better able to find and hold a satellite lock. Once again, this could all be my perception and/or related to the user interface. Perhaps Garmin can/will improve the GPSMAP 76 in future firmware releases. Hard to say...

 

I'm still debating whether to keep the GPSMAP 76. If I do keep it, I'll then have to decide whether or not to keep the Magellan or sell it. Had anybody else here moved from a Magellan receiver to a Garmin unit? Comments?

[Guest morganw]

I was playing with my MAP76 today and found an undocumented feature (at least I can't find it) that should be of interest to most people ... When marking a waypoint, press the menu button and this will let you have the GPS do position averaging for that waypoint. This may help those of you who seem to have a bit less waypoint accuracy... By the way, if you are comparing units and their ability to navigate to waypoints, in the absence of an ABSOLUTE reference there is really no way to know which unit is correct. Those kind of tests are terribly inaccurate. To do it properly you would have to find a USGS marker and base your measurements around THAT. Thank you drive through.

[Guest gstrong1]

My main concern as far as geocaching goes, is that whatever waypoint or set of co-ordinates I post on a cache page are points that others will be able to navigate to & find the cache.If I go to a USGS survey marker & compare numbers that I get, it does not take into account the surroundings at the cache area.Tree cover,etc. I've placed 14 caches & taken the posted co-ordinates off my III Plus, and after 150 or so logged finds at my caches, I haven't had any complaints yet.To me that says my numbers are pretty good.

 

------------------

Gary "Gimpy" Strong

Rochester,NY