[Geowanking] Cheap post-process DGPS - why not?

[KEGan]

Question. If you take a "consumer" GPS, and walk/drive along a path many
times enough. And you could somehow average up all those readings ... would
the average gives you accurate results ?


On 8/6/07, stephen white <steve at adam.com.au> wrote:
>
> On 06/08/2007, at 11:13 AM, Ben Discoe wrote:
> > 5. Using the timecode to correlate, subtract the second unit's
> > drift from the first unit's coordinates.
>
> I can't see how you would do this, because you wouldn't be able to
> tell the difference between movement and drift. The second unit would
> be drifting around at random, rather than having a fixed offset that
> you can add or subtract from the first unit.
>
> > But it should be a really simple operation to subtract one track's
> > offset from another.  Is there some reason this simple approach
> > wouldn't work?  Is there some FOSS which will do it?
>
> I would need to know the situation where you need that level of
> accuracy before I could recommend a range of possible solutions.
> There are basically no solutions that let you walk around with
> accurate tracking no matter how much you spend. You need to pick the
> solution based on the strong points, then wrap the rest of the
> package around fitting to those points.
>
> For example, I use orthorectified aerial maps along with photographs
> to get about 5cm accuracy at selected points. That technique doesn't
> work indoors (obviously) so I have to shift to other methods like
> camera calibration and triangulation to extrapolate a series of
> photographs through scenes. This too would not work for extended
> scenarios due to accumulative error.
>
> The combination of the two inferior methods achieves what I want as
> the aerial imagery provides the broad scale accuracy, limiting the
> indoors extrapolations to short stretches from the front door.
>
> --
>   steve at adam.com.au
>
>
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