[Geomoose-users] Setting buffer select units

[Dan Little]

The performance impact is not TERRIBLE but that also depends on hardware capability and user load.  Even serving 200+ layers, not every user is requesting every layer for every map draw.

Web Mercator is okay, but there are also other projections that look good at that particular spot in the country (I'm thinking something in the neighborhood of an Albers Equal Area Conic).  If your main calculation is based on water bodies within a certain distance then you may very seriously consider storing the data in a different projection, otherwise the calculation that does the radius based search will need to do something like this:

1) Project the center to something in meters or feet.
2) Buffer that point.
3) Project the resulting polygon in to WGS84
4) Then do the search.

This is all assuming you're looking for absolute correctness...  If Brent isn't too busy he might chime in as I know he stores everything in WGS84 and reprojects it on the fly.

>
>From: Dara Olson <dolson at glifwc.org>
>To: Dan Little <danlittle at yahoo.com>; geomoose-users at lists.sourceforge.net
>Sent: Tue, April 27, 2010 1:58:36 PM
>Subject: Re: [Geomoose-users] Setting buffer select units
>
> > 
>
>
>We are using GeoMoose 2.2.  Our data 
>covers three states (Michigan, Minnesota & Wisconsin), so we have all 
>of our postgis data in WGS84.  We want to 
>eventually view the data in webmercator, but we are concerned 
>with speed/performance because we would be reprojecting a lot of layers on the 
>fly.  Currently we have over 200 layers with many more layers to be 
>added.  Will reprojecting that many layers significantly effect 
>performance?  Or would it be better to decrease accuracy in measuring 
>distance and calculating acreage because of the projection (WGS84)?  
>We would using the buffer tool for selecting waterbodies within a certain 
>distance.  Any thoughts or suggestions would be greatly 
>appreciated!
>Miigwech!
>Dara  
>----- Original Message ----- 
>>From: Dan Little 
>>To: Dara Olson ; geomoose-users at lists.sourceforge.net 
>>Sent: Tuesday, April 27, 2010 11:54 
>>  AM
>>Subject: Re: [Geomoose-users] Setting 
>>  buffer select units
>>
>>
>>Hm.. yes, there is.  What version of GeoMOOSE are you using? 
>>   Is there any chance you can use a meters-based projection instead? 
>>   By doing the conversion from DD to a measure unit is a real fallacy 
>>  because it changes DRASTICALLY based on where on the planet the user is trying 
>>  to measure.
>>
>>>
>>>From: Dara 
>>>    Olson <dolson at glifwc.org>
>>>To: geomoose-users at lists.sourceforge.net
>>>Sent: Tue, April 27, 2010 11:05:27 
>>>    AM
>>>Subject: >>>    [Geomoose-users] Setting buffer select units
>>>
>>> >>> 
>>>Is there a way to set buffer select units different 
>>>    than the ground units defined in the mapbook?  I am using WGS84 (4326) 
>>>    and would like to buffer select based on meters, feet or miles and not 
>>>    degrees.
>>>Any help would be greatly appreciated.
>>>Dara
>>


      
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