I’m new to QGIS, apologies if this posted is incorrectly.
I’m trying to map the water system of my community. They had an engineer provide an AutoCAD drawing several years back that have a lot of the system intact, but along with a lot of other info I don’t need. I imported the whole thing into QGIS and exported various layers I need as shapefiles. I then added the shapefiles to a QGIS project that includes an OpenStreetMap layer. Nothing showed when zoomed in to the community, so I “zoomed” out and out and finally found found the shapefiles rendered completely outside the OpenStreetMap layer (i.e. its a little rectangle) and to the right (east) also about 4-5 times the size of the entire OpenStreetMap layer showing the whole world.
I’ve researched this all day trying to find what I did wrong and how to correct with no joy. I’d appreciate any suggestions on how to address. I’m bull headed, but at the point of throwing up my hands and walking away. Thanks for any suggestions.
TomH
Hey Tom,
What version of QGIS and on what OS?
Several things to look at:
1) The CRS of the source file
2) The CRS and on-the-fly projection settings of the QGIS project itself
3) The CRS of the output shapefiles
The trouble sometimes with CAD files is that they can be created in unprojected space. I have run into this on multiple occasions, especially with older drawings. Does the AutoCAD file (DWG or DXF?) render where it should when viewed with OSM layers? Does the AutoCAD file have a projection system defined?
Another thing you can look at is the .prj file associated with your output shapefiles. You can open this in any text editor. It will have the projection definition for that layer.
Let us know...
Best Regards,
James
On Aug 23, 2018, at 20:42, Tom Holz <tlholz@me.com> wrote:
I’m new to QGIS, apologies if this posted is incorrectly.
I’m trying to map the water system of my community. They had an engineer provide an AutoCAD drawing several years back that have a lot of the system intact, but along with a lot of other info I don’t need. I imported the whole thing into QGIS and exported various layers I need as shapefiles. I then added the shapefiles to a QGIS project that includes an OpenStreetMap layer. Nothing showed when zoomed in to the community, so I “zoomed” out and out and finally found found the shapefiles rendered completely outside the OpenStreetMap layer (i.e. its a little rectangle) and to the right (east) also about 4-5 times the size of the entire OpenStreetMap layer showing the whole world.
I’ve researched this all day trying to find what I did wrong and how to correct with no joy. I’d appreciate any suggestions on how to address. I’m bull headed, but at the point of throwing up my hands and walking away. Thanks for any suggestions.
TomH
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James,
Thanks for responding. I’ve tried on QGIS 3.2 and 2.18. I’ve used my Mac. I have a windows10 laptop I could try it on, but haven’t yet. Don’t see it having different result. Following research, when I imported I set project CRS to WGS84, on the fly and for the output files. I don’t know how to check the dwg file for a CRS. I suspect they used a local reference, though there is a grid reference layer with lateral lines marked E2500, 3000, 3500, 4000, and 4500, one vertical line is marked at the lateral cross as E6000, 5500, 5000, 4500, and 4000 That isn’t a mistype, both are marked “E”.
At this point, I’m thinking of just exporting into raster format, importing, and just digitizing the info.
Thanks again,
Tom
On Aug 24, 2018, at 6:51 AM, James Wood <jwood911@gmail.com> wrote:
Hey Tom,
What version of QGIS and on what OS?
Several things to look at:
1) The CRS of the source file
2) The CRS and on-the-fly projection settings of the QGIS project itself
3) The CRS of the output shapefiles
The trouble sometimes with CAD files is that they can be created in unprojected space. I have run into this on multiple occasions, especially with older drawings. Does the AutoCAD file (DWG or DXF?) render where it should when viewed with OSM layers? Does the AutoCAD file have a projection system defined?
Another thing you can look at is the .prj file associated with your output shapefiles. You can open this in any text editor. It will have the projection definition for that layer.
Let us know...
Best Regards,
James
On Aug 23, 2018, at 20:42, Tom Holz <tlholz@me.com> wrote:
I’m new to QGIS, apologies if this posted is incorrectly.
I’m trying to map the water system of my community. They had an engineer provide an AutoCAD drawing several years back that have a lot of the system intact, but along with a lot of other info I don’t need. I imported the whole thing into QGIS and exported various layers I need as shapefiles. I then added the shapefiles to a QGIS project that includes an OpenStreetMap layer. Nothing showed when zoomed in to the community, so I “zoomed” out and out and finally found found the shapefiles rendered completely outside the OpenStreetMap layer (i.e. its a little rectangle) and to the right (east) also about 4-5 times the size of the entire OpenStreetMap layer showing the whole world.
I’ve researched this all day trying to find what I did wrong and how to correct with no joy. I’d appreciate any suggestions on how to address. I’m bull headed, but at the point of throwing up my hands and walking away. Thanks for any suggestions.
TomH
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Qgis-us-user@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/qgis-us-user
Good morning - my gut says it was digitized in a local grid vs something useful. Which means you'll probably have to re-digitize it.
There are some tools in GRASS that might help - granted I've not used them but v.transform might give you the chance to warp it back to the right location. You'd have to know a few things like the shift/scale/rotation to get it to where you need it to be. Which - hopefully it's all digitized in CAD correctly scaled.
https://grass.osgeo.org/grass75/manuals/v.transform.html
On 08/23/2018 09:42 PM, Tom Holz wrote:
I’m new to QGIS, apologies if this posted is incorrectly.
I’m trying to map the water system of my community. They had an engineer provide an AutoCAD drawing several years back that have a lot of the system intact, but along with a lot of other info I don’t need. I imported the whole thing into QGIS and exported various layers I need as shapefiles. I then added the shapefiles to a QGIS project that includes an OpenStreetMap layer. Nothing showed when zoomed in to the community, so I “zoomed” out and out and finally found found the shapefiles rendered completely outside the OpenStreetMap layer (i.e. its a little rectangle) and to the right (east) also about 4-5 times the size of the entire OpenStreetMap layer showing the whole world.
I’ve researched this all day trying to find what I did wrong and how to correct with no joy. I’d appreciate any suggestions on how to address. I’m bull headed, but at the point of throwing up my hands and walking away. Thanks for any suggestions.
TomH
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Qgis-us-user@lists.osgeo.org
https://lists.osgeo.org/mailman/listinfo/qgis-us-user
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