Drakensberg Caves GPS Co-ordinates

03 Feb 2016 21:21 #66837 by ghaznavid
I have sent an email to Dave re Icidi Cave/Pass.

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04 Feb 2016 14:02 #66861 by BobbyStanton
Sometimes the only way to resolve these issues is to see the locations of the gps coordinates in relation to the surrounding terrain. Here are some satellite images with the cave coordinates plotted on them and contour lines included.




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04 Feb 2016 15:21 #66863 by ghaznavid
@Bobby: haven't seen you on the forum for ages! Welcome back :thumbsup:

What software do you use to get the contours on satellite images?

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04 Feb 2016 22:42 #66877 by ASL
Does anyone have the distance between Crows Nest cave and Infidi Cave?

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04 Feb 2016 23:14 #66879 by Smurfatefrog

ASL wrote: Does anyone have the distance between Crows Nest cave and Infidi Cave?

Should be 9 or 10km following mostly an escarpment edge route
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05 Feb 2016 07:15 #66882 by ghaznavid
The easiest line between the 2 would be a bit further, you head inland at the Singati ridge, and up the river behind Ifidi Pass. But I suspect that that line isn't much more than 10km. Ifidi Cave is a lovely cave - well worth the effort.

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05 Feb 2016 09:23 #66886 by mayake

ghaznavid wrote: @Bobby: What software do you use to get the contours on satellite images?

:thumbsup:
Good question

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05 Feb 2016 09:34 #66887 by AndrewP
Looks to me like a 1:10000 orthophoto map

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05 Feb 2016 10:51 #66890 by BobbyStanton
The satellite imagery is Google Earth. Microsoft Virtual Earth is usually better but had some cloud cover in the wrong place. You need a good GIS (Geographic Information System) to place layers of spatial information and to look after the various projections and datums while doing this. I suggest QGis (Quantum GIS) which is open source ie. free. It has a steep learning curve for a beginner however. You also need to brush up on your knowledge projections before starting out.
These pictures have a base projection known as Spherical Mercator which is what most available satellite imagery is in. ie. the earth is assumed to be spherical instead of spheriodal and the coordinates are in the Mercator projection. This allows Google or MS Virtual Earth to calculate locations and distances very quickly as you pan and zoom the image in your browser. The contours are from the Surveyor-General (or whatever they are called now) and are also free. They are in WGS84 or unprojected. The cave coordinates were picked off the previous posts (also presumed to be WGS84) and QGis slapped it all together and looked after the different projections so everything lined up. QGis has a plugin that will download various satellite imagerys for the view that you are mapping.
If you have got the time and the inclination to learn all of this terminology I would say it is not rocket science and doable by anyone. It is all available on the internet.
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05 Feb 2016 11:26 #66892 by ghaznavid

BobbyStanton wrote: It is all available on the internet.

I have tried to find the free downloads, but never had any luck. Could you provide a link by any chance?

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