[OSM-talk] High-Precision GPS Survey Equipment?

[Andy Robinson (blackadder-lists)]

Ævar Arnfjörð Bjarmason wrote:
>Sent: 25 August 2008 6:22 PM
>To: simon at mungewell.org
>Cc: osm
>Subject: Re: [OSM-talk] High-Precision GPS Survey Equipment?
>
>On Mon, Aug 25, 2008 at 4:02 PM,  <simon at mungewell.org> wrote:
>> Hi Ian,
>> How much precision do you want/need? And apart from the fun of it, does
>it
>> actually benefit OSM going to these lengths?
>
>My fairly accurate Garmin 60CSx is still wildly inaccurate when I
>position myself at the corner of a building and try to measure its
>dimensions since the building and the surrounding blocks most GPS
>signals. So more accurate surveying equipment would for one thing be
>more useful in getting data of regular quality in areas where there's
>bad reception.
>

The way surveyors get around this problem (yes even the best GPS systems
cant see around corners) is to take 8 waypoints by sighting down the edge of
a building (2 points for each side). You can then draw the shape where the
lines intersect. This is how the Ordnance Survey do it for instance (using
an optical square to improve accuracy).

>There's also the whole use case of mapping things with <5m accuracy
>where most GPS units start being very inaccurate.
>
>_______________________________________________
>talk mailing list
>talk at openstreetmap.org
>http://lists.openstreetmap.org/listinfo/talk
>
>No virus found in this incoming message.
>Checked by AVG - http://www.avg.com
>Version: 8.0.138 / Virus Database: 270.6.7/1632 - Release Date: 25/08/2008
>7:05 AM