accuracy for point of query mode

[Ken Lord]

Hi Janeks,

Have you tried adjusting the TOLERANCE and TOLERANCEUNITS parameters
for your point layer in your mapfile?

There are a few settings for the units, two of which are meters and
pixels.  You can read more about it here:

http://mapserver.gis.umn.edu/docs/reference/mapfile/layer

If your map has a wide range of scales where it is viewed and queried,
I'd tend to set the toleranceunits as pixels, and the tolerance to 1
or 2.  Zoomed out you may find you get many results back from a query
especially if your data is dense. But if you set the units as meters
(or similar) you may appear to be querying right over a point when the
query coordinate is actually too far from the coordinates of the
target point.

If your point data is fairly regularly spaced, and your users won't be
zooming in and out as much, then for me it feels better with the units
set to meters ... however when zoomed in close, you may get results
returned when querying far away from where a point is drawn on the map
because it is still within the tolerance distance.

If you play with these settings, you'll find a happy medium in there
somewhere that returns results in a consistant manner for your map.

Cheers,
Ken Lord
Vancouver BC


On 12/22/05, Janeks Kamerovskis <janeks.kamerovskis at silva.lv> wrote:
> Hi!
>
> I faced with problem in subj. when doing queries on point layer.
>
> I seems that user should point to exact pixel to get query on point layer,
> because I got info on point just in very rear cases.
>
> But stop ...
> It could be also problem of my javascript on client side -  I should to make
> some debugging ...
>
> But anyway is it possible to change/specify accuracy for point of query
> mode.
>
> Janeks
>