Orienteering with GPS, compass....no map

[+Woodstramp]

Didn't know exactly where a question like this would fit in the forums, but because you Benchmarker folks seem to be more technically oriented toward standards of benchmarking, surveying,maps and such I decided this would be the one to post it in. Moderators feel free to move it if need be.

 

I remember the basics of triangulation using a compass and map from the scouts a zillian years ago. I've never really needed or used a topo to navigate the places I like to go to. Mainly just a compass....head in and then 180 back. Here in Bama things are not really spacious or remote enough to really need classic orienteering stuff. At least for me. (Now watch me get lost for the first time. )

 

What I'm trying to figure out is how to waypoint a distant object using a lensatic typw compass and a GPS (minus a Topo program onboard). I tote a compass in the GPS bag just in case. In standard topo/compass orienteering you can triangulate your unknown position with the map/compass or triangulate the position of distant places if your postion is known. The GPS will show you exactly where you are at any time as long as it's working, but I'd like to figure out how to triangulate something in the distance and store the waymark in the GPS. Say I'm hiking and I see something cool in the distance and would like to store that for a later adventure.

 

Magnetic declination around here is not that big of deal. Just a few degrees......that leads to another question....

 

If you set your GPS from "True North" to "Magnetic" are they internally programmed to compensate for varying degrees of declination? Like here in the this part of Bama declination adjustments are only a few degrees, but another state it would be off several degrees. Do GPS programmers account for this? I would guess so, but not totally sure.

 

Thanks.

[+jwahl]

On the magnetic declination question. Garmins and I suspect others have an internal model of the mag dec and so do "look up" the value for your area. This can usually be viewed on one the Garmin setup screens also. I have found it to usually be within a degree or so. You can check it with one of the online magdec calculators such as is found on the NGS web site.

 

NGS Mag Dec page

 

- jlw

 

 

Magnetic declination around here is not that big of deal. Just a few degrees......that leads to another question....

 

If you set your GPS from "True North" to "Magnetic" are they internally programmed to compensate for varying degrees of declination? Like here in the this part of Bama declination adjustments are only a few degrees, but another state it would be off several degrees. Do GPS programmers account for this? I would guess so, but not totally sure.

 

Thanks.

[+Klemmer]

On the triangulation subject, you might want to browse this thread (also on this forum). It is sort of the opposite you were asking about, maybe. But if you take one bearing to an object, walk a decent about at right angles to it, you can calculate (or map) it's location easy enough. The accuracy you can end up with may be good enough for your purposes.

Edited April 17, 2008 by Klemmer & TeddyBearMama

[+GEO*Trailblazer 1]

My experience.

 

I was taught from a youth to Orient without the use of map,compass or GPS.

Using local objects for reference points and calculating distances just came secondary.

You know about how far something is by the experience you have in walking or hiking those type areas.

When you have to carry out a mule deer you better.

 

Or maybe it is a gift to be able to do this I am unsure because it is a part of my being.

I have Oriented across the whole Nation but not everywhere...yet.

Maybe I was Merriwether Lewis in my past life or by the nature of things and evolution I got that certian gene.

 

It is like the mystery of Magnetic North.

Magnetic??

MSNBC Mystery solved

Pole reversal

 

I have an internal compass that automaticaly knows where north is.

I almost always take the other goodies but I can still find something if I have a general description of an area.

The more detailed the better of course.

 

It seems easy to load up everthing and see yourself live on topo maps and others now days and sometimes I tend to let the equiptment guide without paying attention to details.

This can cause a problem if you are not keeping yourself Oriented.

 

I take everything but almost always can find things with just the GPS and a written description of what it is I am suppose to be looking for.

Then if I can't find it I fire up the laptop look at the data sheet and or old description,cache page or what ever and look a little harder.

 

Well I could go on forever but better cut it off for now.

It is all very intersting to learn and study from to see where in the heck am I?

 

If you are using a lensatic with a GPS I would set the GPS to magnetic north.

If you are using maps I would set it to whichever map datum the map is in as well.

 

Then take sighting do your calculating,enter it in the GPS and see how well you did.

After a few times you will get better at it.

 

I hope that answers your question.

[+Black Dog Trackers]

Woodstramp -

 

For your kind of project, I suggest not using a GPSr at all; your compass and a tape measure will provide much better accuracy.

 

Do what Klemmer said - and the points of it are to make sure that you are walking at an exact right angle, from point A to point B, and to measure very accurately with a tape measure how far you walk. At point B take a bearing as accurately as you can toward your point of interest.

 

Pick your point A so that the right angle view points to either some distant landmark or a tall stick you stick in the ground.

 

It is possible to use a GPSr to establish an angle more accurate than your compass, but you will have to walk toward your point of interest quite far from both point A and point B to establish waypoints C and D. You can estimate this distance by doing some experiments with your compass to see how accurately you can measure angles. A GPSr has a zone of 10 to 20 feet in diameter so you would have to go at least as far away so that your compass would have a similar error level.

[tosborn]

Here's a method to do what the original poster wants to do with a GPS receiver and a compass. It should work with mapping and non-mapping GPS receivers as long as they have a "Project Waypoint" capability.

 

1) Record a waypoint at your first location...call it "A".

 

2) While still at "A" take an azimuth on the distant point with the compass. Using the "Project Waypoint" feature of the GPS (for example on the Garmin 60CSx), project a new waypoint from "A" using the azimuth just determined and a distance large enough to extend well beyond the distant point. Call the newly projected waypoint "B".

 

3) Go to another location where the distant point can observed and record a waypoint there...call it "C".

 

4) While still at "C" take an azimuth on the distant point. Using the "Project Waypoint" feature of the GPS project a new waypoint from "C" using the azimuth just determined and a distance large enough to more than extend beyond the distant point. Call the newly projected waypoint "D".

 

5) Create a route in the GPS using waypoints in the following order: A, B, D, C. The point where the route crosses itself is the location of the distant point. Zoom in and create a waypoint at the point of crossing.

 

If your compass is not corrected for magnetic declination, make sure your GPS 's "North Reference" is magnetic.

 

Of course, you could also do the math for an Azimuth/Azimuth Intersection (Foresection) if you also bring along a calculator or laptop.

 

Edited April 18, 2008 by tosborn

[+Woodstramp]

 

NGS Mag Dec page

 

- jlw

 

 

If you set your GPS from "True North" to "Magnetic" are they internally programmed to compensate for varying degrees of declination? Like here in the this part of Bama declination adjustments are only a few degrees, but another state it would be off several degrees. Do GPS programmers account for this? I would guess so, but not totally sure.

 

Thanks.

Thanks for the link. I was thinking that they must've figured how to automatically fix that.

[+Woodstramp]

On the triangulation subject, you might want to browse this thread (also on this forum). It is sort of the opposite you were asking about, maybe. But if you take one bearing to an object, walk a decent about at right angles to it, you can calculate (or map) it's location easy enough. The accuracy you can end up with may be good enough for your purposes.

 

Thanks for the link. If I understand what was going on there at that thread they were using a projection function on the GPS for a distant cache. What I would like to do is simular, but I' assuming they gave projected info for others to follow. What I'd like to is.....well I'll just give a paractical example...

 

I'm out hunting on a ridge. Great view, beatiful day,etc. Drought in the SE these last two years has dried up local horse hay supplies to nothing. We're low at the house. I'm glassing for squirrel when down in valley I spot a very large barn packed with hay.... I'd like to check with that guy later to see if he'd like to sell a few bales. His barn is in a large , flat wooded area. Compass sighting says 46 degrees and what reckons to be a mile or two away. I've got a compass and my (non-Topo'd) GPS is set to read magnetic. I can't really make out roads and such because of the cover. How do I way mark his place as a waypoint so I can drive up later to have a chat?

[+Woodstramp]

Here's a method to do what the original poster wants to do with a GPS receiver and a compass. It should work with mapping and non-mapping GPS receivers as long as they have a "Project Waypoint" capability.

 

1) Record a waypoint at your first location...call it "A".

 

2) While still at "A" take an azimuth on the distant point with the compass. Using the "Project Waypoint" feature of the GPS (for example on the Garmin 60CSx), project a new waypoint from "A" using the azimuth just determined and a distance large enough to extend well beyond the distant point. Call the newly projected waypoint "B".

 

3) Go to another location where the distant point can observed and record a waypoint there...call it "C".

 

4) While still at "C" take an azimuth on the distant point. Using the "Project Waypoint" feature of the GPS project a new waypoint from "C" using the azimuth just determined and a distance large enough to more than extend beyond the distant point. Call the newly projected waypoint "D".

 

5) Create a route in the GPS using waypoints in the following order: A, B, D, C. The point where the route crosses itself is the location of the distant point. Zoom in and create a waypoint at the point of crossing.

 

If your compass is not corrected for magnetic declination, make sure your GPS 's "North Reference" is magnetic.

 

Of course, you could also do the math for an Azimuth/Azimuth Intersection (Foresection) if you also bring along a calculator or laptop.

 

I'll print your post out and give it a try at next opportunity. Wife just got out of hospital... might be a few days. Thanks.

[+Woodstramp]

Here's a method to do what the original poster wants to do with a GPS receiver and a compass. It should work with mapping and non-mapping GPS receivers as long as they have a "Project Waypoint" capability.

 

1) Record a waypoint at your first location...call it "A".

 

2) While still at "A" take an azimuth on the distant point with the compass. Using the "Project Waypoint" feature of the GPS (for example on the Garmin 60CSx), project a new waypoint from "A" using the azimuth just determined and a distance large enough to extend well beyond the distant point. Call the newly projected waypoint "B".

 

3) Go to another location where the distant point can observed and record a waypoint there...call it "C".

 

4) While still at "C" take an azimuth on the distant point. Using the "Project Waypoint" feature of the GPS project a new waypoint from "C" using the azimuth just determined and a distance large enough to more than extend beyond the distant point. Call the newly projected waypoint "D".

 

5) Create a route in the GPS using waypoints in the following order: A, B, D, C. The point where the route crosses itself is the location of the distant point. Zoom in and create a waypoint at the point of crossing.

 

If your compass is not corrected for magnetic declination, make sure your GPS 's "North Reference" is magnetic.

 

Of course, you could also do the math for an Azimuth/Azimuth Intersection (Foresection) if you also bring along a calculator or laptop.

 

[+Woodstramp]

Here's a method to do what the original poster wants to do with a GPS receiver and a compass. It should work with mapping and non-mapping GPS receivers as long as they have a "Project Waypoint" capability.

 

1) Record a waypoint at your first location...call it "A".

 

2) While still at "A" take an azimuth on the distant point with the compass. Using the "Project Waypoint" feature of the GPS (for example on the Garmin 60CSx), project a new waypoint from "A" using the azimuth just determined and a distance large enough to extend well beyond the distant point. Call the newly projected waypoint "B".

 

3) Go to another location where the distant point can observed and record a waypoint there...call it "C".

 

4) While still at "C" take an azimuth on the distant point. Using the "Project Waypoint" feature of the GPS project a new waypoint from "C" using the azimuth just determined and a distance large enough to more than extend beyond the distant point. Call the newly projected waypoint "D".

 

5) Create a route in the GPS using waypoints in the following order: A, B, D, C. The point where the route crosses itself is the location of the distant point. Zoom in and create a waypoint at the point of crossing.

 

If your compass is not corrected for magnetic declination, make sure your GPS 's "North Reference" is magnetic.

 

Of course, you could also do the math for an Azimuth/Azimuth Intersection (Foresection) if you also bring along a calculator or laptop.

 

 

Well, got a few minutes to go play in the yard. Used the method you posted here. Worked like a charm using the GPS projection function.

 

Thing is it never occured to me that you could use a clear Sliva map compass right on the GPS's screen (like a map. Dummie me. Used the Silva to project bearings too.

 

Just scale projection points and start points so all are visible on the LCD at the same time. Using projection distances of 500' I was able to get within 15 ' of the projected object. Cool.

 

Thanks all.