[Geomoose-users] Scalebar & Measure

[Brent Fraser]

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:bfraser at geoanalytic.com] 
> Sent: Wednesday, May 26, 2010 1:53 PM
> To: Len Kne
> Cc: '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:Paul.Wirth at kniferiver.com]
>>> *Sent:* Saturday, May 01, 2010 9:03 PM
>>> *To:* '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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