Plotting coordinates

Hi Everyone,

I am new to Grasshopper and this is my first post. I'm trying to plot 'x' and 'y' coordinates and for some reason it is plotting along a line rather than seperate values. The spreadsheet just has an 'A' and a 'B' column indexing the 'x' and 'y' values and all text has been removed. Below is the script so far. I would really appreciate some help,

Cheers, J

Replies to This Discussion

Permalink Reply by AB on December 27, 2012 at 2:37pm

james,

It would help if you could add another screenshot with a panel showing the output of the ReadFile Component.... before you do anything to it.

There could be several things going on.... I suspect your list item components are selecting the same items which is why you are getting duplicate data... which causes a linear plot when fed into a Pt component.

Show us what you data looks like and it will be easier to help.

Permalink Reply by James Williamson on December 27, 2012 at 3:42pm

Thanks for your help. You were correct, my list items were selecting the lattitude twice giving me a linear plot! I don't suppose you could help me with another question though? I have managed to plot my x and y coordinates but they appear to be affected by the curvature of the earth and are bunching a bit where they should be more spread out.

Is there any way to correct this in grasshopper? It would be great to hear if there was.

Thanks J

Permalink Reply by Hannes Löschke on December 27, 2012 at 4:59pm

So your coordinates are actually GIS coordinates rather than X-Y cartesian coordiantes?

You can transform coordinates in any way you like with grasshopper. With GIS this is rather a question of which projection system works best for the task. There is no GIS component that does such conversion AFAIK, but you can build your own with GH math. Just need to figure out how to transform your given coordinates to the system of your choice.

Permalink Reply by James Williamson on December 27, 2012 at 5:42pm

Hi Hannes, thanks you for you reply.

I am trying to create a 2d map so am not sure what is the best coordinates for this. At the minute i have plotted decimal WGS84 coordinates, i.e. (Lat) 50.545, (Long) -4.15. It seems that the lattitude is not locally accurate. I am very new to grasshopper and am pretty clueless. I would be amazing if there was a script to convert the coordinates. I dont know if this would be corrected in gHowl with xyz coordinates? This is what i have so far. Any help would be amazing, and appreciate the comments. I would be going around in circles otherwise. J

Permalink Reply by Hannes Löschke on December 28, 2012 at 6:46am

Ok, plotting WGS84 coordinates on a flat surface is not a good way. There is no straight forward way to convert lat/long to a flat projection.

For a local area, you can just project onto a plane that is normal to the WGS ellipsoid. Distortion will grow with the distance to the planes origin. I'm not sure what the Geo->XYZ component does exactly (didn't even know it existed) but my best guess would be something like I just described.

Permalink Reply by James Williamson on December 29, 2012 at 12:55pm

Hi Hannes,

Thank you for you help. I have managed to covert the coordinates so that the project correctly in 2d after doing a bit of research. Thanks again for the help.

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