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'Surveying. (sas: Extra GPS receivers?)'
1999\07\28@145010 by Barry King

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Sorry about the double post.  Itchy trigger finger :)

Adam,

Let's go back to original problem.  We want to map a trail.  Let's
assume that we've got a 7.5 minute topo map.  On CD, if that helps.

Can I do inertial navigation, by integrating the output of a bike
speedo and the output of a digital compass using the PIC as a data
logger, and post processing?  How about a special pickup using the
bike wheel as a distance measurement wheel, and the compass?

How about Loran, which is not intentionally crippled?

How about just good old fashioned orienteering / surveying methods by
triangulation to known fixes?  Is there an advantage to having a
smart data collection system to do calculation on the fly?

1999\07\28@153032 by Adam Davis

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Barry King wrote:
> Let's go back to original problem.  We want to map a trail.  Let's
> assume that we've got a 7.5 minute topo map.  On CD, if that helps.
>
> Can I do inertial navigation, by integrating the output of a bike
> speedo and the output of a digital compass using the PIC as a data
> logger, and post processing?  How about a special pickup using the
> bike wheel as a distance measurement wheel, and the compass?

I've thought about that, but I don't know any inexpensive digital compasses
which would give me, say 1 degree of resolution and accuracy.  Secondly, I'd
then need to find altitude seperately.  I've thought about simple measuring the
angle of the front wheel in relation to the rest of the bike, and the distance
it travels, but, again, altitude becomes a problem, and I shudder to think about
the math involved.
Altitude matters only because if I go stright, turn right, go down a hill, and
turn right again to end up at the beginning, I will end up with a map where the
end is nowhere close to the beginning, even though they are the same point.  The
distance going downhill is not directly translated into forward movement.  (ie,
15 feet of wheel movement, and I may have only moved horizontally by 10 feet)  I
could have a tilt sensor, but that is an added variable to the entire equation
which is neatly solved with GPS.

>
> How about Loran, which is not intentionally crippled?

Haven't thought about it much.  It's not considered inexpensive to me.  I
imagine I does not give altitude...

>
> How about just good old fashioned orienteering / surveying methods by
> triangulation to known fixes?  Is there an advantage to having a
> smart data collection system to do calculation on the fly?

Yes, I'm only doing this for fun, as part of a hobby.  I don't want to survey
the trails, I want to measure my performance, and see a map of where I was, and
how I did on any given trail.  So I would rather spend an hour biking the trail
and have the data at the end, than going out with equipment and surveying the
trail.

-Adam

1999\07\28@155333 by Adam Davis

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I see, however, that that's where a topo map would come in...  I suppose
altitude could be determined afterwards in post processing...

-Adam

1999\07\28@225639 by Anne Ogborn

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Barry King wrote:
>
> Sorry about the double post.  Itchy trigger finger :)
>
> Adam,
>
> Let's go back to original problem.  We want to map a trail.  Let's
> assume that we've got a 7.5 minute topo map.  On CD, if that helps.
>
> Can I do inertial navigation, by integrating the output of a bike
> speedo and the output of a digital compass using the PIC as a data
> logger, and post processing?  How about a special pickup using the
> bike wheel as a distance measurement wheel, and the compass?
>

Certainly for enough money you can get a dead reconning system
to attach to a GPS receiver, and they do improve accuracy.
I don't know aobut vibration. A mountain bike is not a stable
platform.

> How about Loran, which is not intentionally crippled?

Don't think it's as accurate as GPS. Loran was intended as
a long range navigation system.

Have you verified that you actually do have an accuracy problem with
simple USCG corrected GPS?

--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html

1999\07\29@171449 by Love Shack

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Adam

I've been looking into doing exactly the same thing (mapping Mtb tracks)...

Have you looked into Differential GPS.  For a site with plans for a couple
of homemade units go to  http://home1.gte.net/clseng/DGPS_index.htm

looks mighty good.

Hamish




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