Topography - Surveying - GIS usage

Previous Topic Next Topic
 
classic Classic list List threaded Threaded
10 messages Options
Reply | Threaded
Open this post in threaded view
|

Topography - Surveying - GIS usage

aefavant
Hello there, Tony here, speaking from Rio de Janeiro, Brazil.

I am very new to LibreCAD and I installed it looking for ways to not use the autodesk solutions, So far, I was able to tweak a few lines and angles :)
What I can say about Libre is that it is super light, fast and user friendly!

Please let me know if htere are others like me. I reall want to know if is there support for topo / gis / land survey in LibreCAD and HOW TO USE THEM.

Many thanks
cheers
Reply | Threaded
Open this post in threaded view
|

Re: Topography - Surveying - GIS usage

dellus
There are no special tools for topo / gis / land survey in LibreCAD, except maybe Plugins - ESRI shapefile. This seems to have something to do with the subject, but I don't know how to use it.
In the settings for Angular units there is Surveyor's units, whatever that is.
In the past there have repeatedly been announcements by some users to contribute some development in that field, but there never has been any outcome.

Still, when you get to special questions, ask them here. Somebody might have answers.

 
Reply | Threaded
Open this post in threaded view
|

Re: Topography - Surveying - GIS usage

LordOfBikes
Administrator
There are also issues when you work in real world coordinates far away from absolute zero point.
This is an issue with computation tolerances when relative small objects are placed at really big coordinates.
Then some tools can't find intersections or tangent points.
I think these issues are discussed here in the forum from time to time and you may find them using the search function.
Reply | Threaded
Open this post in threaded view
|

Re: Topography - Surveying - GIS usage

Moult
Many DWGs and DXFs provided by surveyors contain 3D survey points nowadays. If this is the case for you, it might be worthwhile not to use LibreCAD as LibreCAD will only show the 2D data. An alternative is to use Blender's DXF importer. Once imported, you can use the BlenderGIS plugin to perform some geolocation, and generate TINs from the survey via its Delaunay Triangulation tool.

I'm surprised that @LordOfBikes mentions that LibreCAD has issues with real world coordinates. I would've expect LibreCAD to handle it. My current workflow is to use AutoCAD to offset the survey from real world coordinates to a known origin point (usually a corner of the surveyed property site boundary). I was hoping that LibreCAD could do this too but maybe I am wrong. @LordOfBikes, is there any way to offset DWGs/DXFs to solve this issue? Ideally it could be something headless or via a quick script with minimal dependencies, so that the same solution could be used for other apps too.
Reply | Threaded
Open this post in threaded view
|

Re: Topography - Surveying - GIS usage

dellus
Of course you can move the populated area of an opened file with far off coordinates to somewhere near absolute zero. If you do this as the first step it might be enough to secure further more complex operations to run within acceptable coordinate limits. To be tested.
Reply | Threaded
Open this post in threaded view
|

Re: Topography - Surveying - GIS usage

Moult
Can this be tested? I am afraid that even in the import process the points may be incorrectly positioned. I know that this problem occurs in Blender, so it needs to be moved prior to import.
Reply | Threaded
Open this post in threaded view
|

Re: Topography - Surveying - GIS usage

perepujal
I, time to time, get topographic data with a Leica geostation and import it as points into LibreCAD via the plugin "Read ascii points" as a help to draw complex existing buildings.

I have never encountered a problem where the points weren't at their place, I usually "declare" the station to be at 100m,100m, so the points I get are always positive and usally in the range of 70 to 130 meters away from 0, but few unusual times I had to declare stations beign more than 1 kilometer from 0 and never encountered a problem. Maybe the precision problems starts far away?
Reply | Threaded
Open this post in threaded view
|

Re: Topography - Surveying - GIS usage

Moult
@perepujal - yes, I believe the precision problems we're talking about is when points are absolutely positioned in the world, using a coordinate reference system, which is a different scenario to what you've described.
Reply | Threaded
Open this post in threaded view
|

Re: Topography - Surveying - GIS usage

LordOfBikes
Administrator
Here is an old post where I tried to explain this issue.
https://forum.librecad.org/snap-intersection-circle-line-tp5716171p5716187.html

Where exactly the limits are is hard to say, as said in the linked post, it's the relation between object size and relocation from absolute zero.
So moving the drawing towards the origin is the recommended workaround for this issue.

I understand, that the data sources deliver real world coordinates and sometimes it is absolutely needed or easier to work with these coordinates.
But this is a common issue in computer math and needs special handling to solve.
There have been several announcements in the past, that people try to work on GIS/COGO functionality for LibreCAD, but it seems to be not that easy, there are still no results.
Reply | Threaded
Open this post in threaded view
|

Re: Topography - Surveying - GIS usage

flywire
In reply to this post by aefavant
Try FreeCAD.