Geo caching

Most GPS units are good to within 10 feet now. When you get to the coordinates you know you are pretty close. Visualize a 10 foot square and start hunting. Hope this helps.

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I stumbled on to a geocache site while looking for markers.  It was a ammo box under a rock slab.  If your withing 20 feet you should find it .
okey dokey

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		Quote:			Posted by goldigger
	Iseegold; Geo caching is getting very popular, and GPS units are getting better, the professional ones, for surveying CAN be as close as 18 inches! But they are expensive. I find the newer units are good but not yet good enough to survey a claim boundary, of which I have several that adjoin other claims.... so far no disputes, we seem to be getting along. Surveys cost too much so GPS accuracy cant improve fast enough for me. Brian AKA goldigger (not a claim jumper)

Hay Bryan,

I am a retired professional surveyor. I am familiar with
all but tha latest survey quality GPS units.

The units today can get far closer than 18 inches. But
it takes checks to insure such accuracy. You can not go
out and take a few readings and stake your professional
standing on it.

In some areas, where property values are very high, and
building off sets are 0.0 feet, you must be with in an inch.

Thet means, you must have equipment that can be within
a few centimeters.

You can get that kind of accuracy if you are a professional.
I know because I've have had to deal with that kind of crap.

But units used by tha general public are generally accurate
to with in about 10 feet. That is a 20 foot circle.

If you use some tricks that surveyors know, you can get
what appears to be accuracy to with in a about 3 feet.

This can be somewhat effected by differences in map
datum used and so on.

Just more details.

But, unless there is a problem, a 20 foot circle is usually
attainable.

That is tryin real hard.

Tabdog


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tabdog;

You have hidden talents!

Yes, I was quoting from something I read, this spring, of course a surveyor HAS to be closer than 18 inches, but, hey, you have to start somewhere.

I was an engineers AIDE in the late 50s, thats a fancy term for Rod Man, but in Geophysical (Seismic) oil exploration. Learned a lot about surveying, enough to study up, to learn more.

Im a hunter-type, that means I learn what I need, when I need it, as opposed to farmer-type who sits down and studies it ALL. (It also means I miss some things.)

None of the GPS equipment, I have, has better than 1 meter accuracy and usually 3 meters. (10 feet.) I had an opportunity to buy a sextant (air type with artificial horizon.) but passed it up... wish I hadnt. Hey, I can find Polaris, Cygnus, Orion.... does it do me any good?

Brian AKA goldigger


Hay bryan,

I started out as a rod man a long time ago.

The survey quality precision is achieved by using dual
receivers. One receiver must be set up on a point that
has a known horizontal and vertical location......... The
error encountered by the receiver on tha known point
can be calculated, and then adjustments made to the
unknown point being located............ There is also the
communication between the units. They can measure
relationships between each other.

But,,,,,,,, that does not guarantee the accuracy, or tha
precision necessary for the requirements.

That is where the surveyor comes in.

A surveyor analyzes error......... Both in precision and
accuracy, which are two different things.

Precision means how close it is.

Accuracy means if it is right or not.

All tha precision in tha world means nothing if measured
from tha wrong datum.

It may be very precisely wrong and inaccurate. But still
precise.

Knowing tha locations of stars can be helpful. You can
always tell direction, if ya can see tha sky.

For survey astronomical sightings to determine a bearing
are usually done with son shots now days.

On the ocean, on a mountain or in tha desert would be
great for star shots. But I personally have never done a
star shot. Just sun shots.

When I was younger, I had chances to buy old brass
transits for little or nothing. But I never did.

Boy, what a dummy Tabdog is?

Happy Huntin,

Tabdog

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		Quote:			Posted by goldigger
	tabdog; I have an idea, for you: I read, somewhere, within the last year... and this discussion brought it back to mind... that was; use 2 GPS units (why not 3 or even 4), take a reading from each, and select a point centered to all the readings - this is supposed to increase accuracy. Ive never tried it, it seems logical, I will find a good benchmark and set it up... later. If it increases the accuracy to 5 feet, its worth the extra effort. As for narrowing the geocache search, one needs to use the best instruments ever made... eyes. Brian AKA goldigger

It can get expensive.

These GPS units must be multi- frequency.
They transmit, like a satalite does, and
comunicates with the other units.

The use of multi units has gone on by tha
military sense before it was made available
to tha public.

The use of more units will not increase the
precission as much as having more satalites
to read, and/or having a good dependable
stationary point close to where you are
locating other points.

But if you have the money to get just two
multifrequency, survey units, you can get
very good results, if used properly.

That includes money for try-pods, shovels,
concrete, rebar. Points must be un-moveable.
You will need a total station, prizm poles
and so on.

Just depends on how much precission you
want.

If you know a few tricks, you can get a lot
closer with some of tha better single frequency
units.

For instance, shots taken in tha same area,
and in a short time period will have a much
better relationship between each other, than
they would have to a map produced coordenate,
or a coordinate produced form any outside datum.

So, there for, you can produce a map with fairly
dependable relationship to what was taken at
that time.  If ya got a got fix on two known
points with some distance between, you can have
a link to other datum, and a bearing.

You could add data by physically measuring points
and intering them into tha map datum.

It is called work in tha survey bussiness. It can be
tricky til ya understand tha requirements, and all
types of error involved.

That is tha reason it is hard ta get ridd of us crusty
old bats. Somebody has ta figger out what went
wrong..... lol

And everybody knows, lawyers and judges just screw
things up for good, so that they are tha only winners.

So, all ya got left ta set thing right is tha crusty old
farts like me.

Happy Huntin,

Tabdog

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