[OSGeo Africa] Problem displaying both Google earth image and farm boundary layers on map canvass

Jeffery Hlongwane jeffhlongs at gmail.com
Fri Oct 11 09:24:43 PDT 2013


>>>I have a limited basic knowledge as far as QGIS is concerned and apologize for lack of clarity. In fact the image is directly from google map installed as stand alone on my computer. I saved the image from Google map and uploaded it on QGIS (georeferencer) as a result it is not from Open Layer plugin.

>>>My intention is to learn how to do this exercise using image saved from stand alone desktop google map. I will deal with Open Layer plugin later for I cannot even access it on my workstation but with my laptop at home I can.  I will check tomorrow if the CRS projections for both layers are appropriately defined.  Thanks for your response.

>>>Regards
>>>Jeffery Hlongwane


On 10/10/13, Gavin Fleming <gavinjfleming at gmail.com> wrote:
> Jeffery
>
> Why are you trying to georeference a google image when you say it is
> already georeferenced? Is the Google image coming in via the OpenLayers
> plugin? If so then it is already in EPSG:3857.
>
> If both layers have the correct CRS defined in their properties, they
> will overlay properly when on-the-fly CRS projection is switched on. So
> check what the native geometries (coordinates) of your datasets are and
> make sure they have the appropriate CRS defined.
>
> Gavin
>
> On 10/10/2013 13:46, Jeffery Hlongwane wrote:
>> Hi
>>
>> I am trying to align google image (georeferenced) with the farm
>> boundaries layer on QGIS. However, my challenge is only one layer
>> appears on map canvas and can only see the other via zoom to extent
>> option which automatically removes previously displayed layer from map
>> canvas. Can you please assist me? For now I can provide the following
>> further details.
>>
>>>>> The software I am using on my machine windows 7 machine is QGIS 1.8
>>>>> Lisboa.  Georeferencing was based on the following coordinates control
>>>>> points from Google Map.
>> Points	X	                  Y	
>> p1	­ - 25°40'40.58"S	 25°40'40.58"S	
>> p2	 -28°23'58.19"E	 25°40'41.81"S	
>> p3	 -28°23'32.75"E	 25°40'57.56"S	
>>
>>>>> When comes to transformation settings I used linear type, resampling
>>>>> method was nearest neighbour and lastly the target srs was EPSG 4326.
>> -Google georeferenced image's Spatial Layer extent :
>> 28.3874623288009538,25.6655111594936081  :
>> 28.4012727306202954,25.6753215312726546
>> Google image spatial reference system : +proj=longlat +datum=WGS84
>> +no_defs
>> Farm boundaries layer extents:
>> On QGIS  : Spatial reference system units : xMin,yMin 26.6218,-27.0627
>> : xMax,yMax 29.8673,-25.1096   Spatial Reference System: +proj=longlat
>> +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +no_defs
>> Original projection details :
>> GEOGCS["GCS_Hartebeesthoek_1994",DATUM["D_Hartebeesthoek_1994",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]
>>>>> I also used checked the box for on the fly option and used WGS84. I've
>>>>> trying for several times and now feel I can give a shout for help.
>>>>> Thank you in advance.
>>
>> Yours Sincerely
>>
>> Jeffery Hlongwane
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>> Africa at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/africa
>
>
> --
> Gavin Fleming
> t: 0218620670
> w: 0218630660
> c: 0845965680
> f: 0866164820
> Paarl
> South Africa
> 18°59'19.6"E 33°44'46.1"S
>
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