[Geomoose-users] Scalebar & Measure
Brent Fraser
bfraser at geoanalytic.com
Thu May 27 12:11:14 EDT 2010
How about omething like:
<tool name="measure" title="Measure" type="internal" action="measure"
geodesic="false"/>
<tool name="measurearea" title="Measure Area" type="internal"
action="measurearea" geodesic="false"/>
Note the default would be true so the implementer would need to turn it off if
they wanted distances on the mapping plane.
Hmm. Does this imply I could have both geodesic AND map measures at the same
time by creating these tools as well:
<tool name="measure2" title="Measure Ground Dist" type="internal"
action="measure" geodesic="true"/>
<tool name="measurearea2" title="Measure Ground Area" type="internal"
action="measurearea" geodesic="true"/>
Brent
Dan Little wrote:
> Probably just make it the default setting inside of the tools.
>
>
> ----- Original Message ----
>> From: Brent Fraser <bfraser at geoanalytic.com>
>> To: Len Kne <lkne at houstoneng.com>
>> Cc: "geomoose-users at lists.sourceforge.net" <geomoose-users at lists.sourceforge.net>
>> Sent: Thu, May 27, 2010 10:02:01 AM
>> Subject: Re: [Geomoose-users] Scalebar & Measure
>>
>> Good.
>
> Should we just hard-code it within Geomoose (as below), or
>> provide a
> configuration parameter in the mapbook?
>
> Brent
>
> Len
>> Kne wrote:
>> Very nice! Worked great and is much simpler than the
>> way I was doing the calculation.
>>
>> Len
>>
>>
>> -----Original Message-----
>> From: Brent Fraser [mailto:
>> ymailto="mailto:bfraser at geoanalytic.com"
>> href="mailto:bfraser at geoanalytic.com">bfraser at geoanalytic.com]
>>
>> Sent: Wednesday, May 26, 2010 1:53 PM
>> To: Len Kne
>> Cc: '
>> ymailto="mailto:geomoose-users at lists.sourceforge.net"
>> href="mailto:geomoose-users at lists.sourceforge.net">geomoose-users at lists.sourceforge.net'
>>
>> Subject: Re: [Geomoose-users] Scalebar & Measure
>>
>> Len(and
>> others interested in measuring),
>>
>> Here's my
>> solution to the measure problem:
>>
>> In main.js somewhere around
>> line 138 add the two lines below marked with a "//BWF":
>>
>>
>> Tools['measure'] = new
>>
>> OpenLayers.Control.GeoMooseMeasure(OpenLayers.Handler.MeasurePath,
>>
>> measureToolOptions);
>> Tools['measure'].geodesic =
>> true; //BWF
>>
>> Tools['measurearea'] = new
>>
>> OpenLayers.Control.GeoMooseMeasure(OpenLayers.Handler.MeasurePolygon,
>>
>> measureToolOptions);
>>
>> Tools['measurearea'].geodesic = true; //BWF
>>
>>
>> Thoughts?
>>
>> Brent
>>
>>
>> Brent Fraser
>> wrote:
>>> Paul, Len,
>>>
>>> Our scale
>> problem is a (mostly) map projection issue. All map projections
>>
>>> introduce distortions in trying to represent a round(ish) Earth on
>> a flat plane.
>>> Mercator is no different: it is like wrapping
>> an up-right cylinder around the
>>> Earth, projecting light from the
>> center onto the cylinder
>> (http://en.wikipedia.org/wiki/Mercator_projection). As you can imagine the
>>
>>> distortions get "worse" the further from the equator. The
>> distortions can be
>>> modeled as a Point Scale Factor. At the
>> equator the Point Scale Factor is 1.0,
>>> at latitude 60 degrees North
>> (or South), the scale factor is 0.5!
>>> So
>> what's the solution? Here's mine:
>>> 1.
>> Enhance Proj4 (and Proj4js) to return the Point Scale factor (given the
>>
>>> projection and a location)
>>> 2. Enhance
>> MapServer and Openlayers to use the Point Scale Factor in
>> calculating distances and scale.
>>> I'm trying to drum up
>> interest, but so no takers....
>>>
>> http://osgeo-org.1803224.n2.nabble.com/Point-Scale-factor-service-td4938743.html
>>>
>> http://osgeo-org.1803224.n2.nabble.com/Re-3265-Scale-dependent-layer-switching-error-with-Mercator-td4966902.html
>>>
>> Best Regards,
>>> Brent Fraser
>>>
>>> Len Kne
>> wrote:
>>>> The scale bar issue with the web Mercator projection is a
>> limitation of
>>>> OpenLayers, the application GeoMOOSE 2.x uses to
>> render the map frame.
>>>> There has been discussion on the
>> OpenLayers site about providing a
>>>> patch (this link offers a
>> patch http://trac.openlayers.org/ticket/1890 )
>>>> in the next
>> version 2.9. I'm sure GM will upgrade to OL 2.9, but not
>> sure there is any schedule in place to do
>> this.
>>>>
>>>>
>>>> The
>> cursor issue is also kind of fun because it seems each browser
>> handles the custom icons differently. Here's the attribute in the
>>
>>>> mapbook which defines the query for the Identify
>> service:
>>>>
>>>>
>>>>
>> cursor="url('cursors/identify2.cur') 9
>> 9,url('cursors/identify2.cur'),auto"
>>>>
>>>> This makes three attempts to draw the cursor,
>> the first offsets the
>>>> mouse click 9 pixels from the top and the
>> left. Firefox can use this
>>>> value and seems to line the
>> mouse click up pretty good with the
>>>> crosshair. However,
>> IE cannot handle the offset adjustment, so it reads
>>>> the second
>> cursor definition. There are tools like AT File Mole which
>>
>>>> can be used to edit the hotspot of a cursor. Attached is
>> the latest
>>>> version I have been using for Identify service,
>> again this seems to line
>>>> the crosshair up pretty well with the
>> mouse click. If you are using
>>>> Safari or Chrome, these
>> setting don't seem to work at all and I would
>>>> recommend not
>> using customer cursors with those
>> browsers.
>>>>
>>>>
>>>>
>> Len
>>>>
>>>>
>>>>
>> *From:* Wirth, Paul [mailto:
>> href="mailto:Paul.Wirth at kniferiver.com">Paul.Wirth at kniferiver.com]
>> *Sent:* Saturday, May 01, 2010 9:03 PM
>>>> *To:* '
>> ymailto="mailto:geomoose-users at lists.sourceforge.net"
>> href="mailto:geomoose-users at lists.sourceforge.net">geomoose-users at lists.sourceforge.net'
>> *Subject:* [Geomoose-users] Scalebar &
>> Measure
>>>>
>>>>
>>>>
>> Two questions:
>>>>
>>>> 1. I have a web Mercator
>> application, and I noticed that the
>>>> scalebar does not display
>> the correct distance. For instance, when the
>>>> scalebar
>> shows a distance of 20 miles, it measures only 13.8 miles. I
>>
>>>> know the measure tools are working correctly, so I assume this
>> is a
>>>> scalebar issue. Any thoughts on how to fix
>> this?
>>>> 2. I think this
>> question was asked before, but I can't seem to
>>>> find it on the
>> e-mail list. With the measure tools, the cursor does not
>> start measuring at the "crosshairs" when the user clicks, but rather in
>>
>>>> the NW quadrant of the crosshairs. Is there a way to
>> change it so the
>>>> measure start point will be on the
>> crosshairs?
>>>>
>>>>
>> ------------------------------------------------------------------------
>>>>
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>>>>
>>>>
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>>>>
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