Localization of a Drawing

[Shawn Billings]

I had great success last week localizing a CAD drawing in J-Field. I imported the CAD file into a Page with an Unknown coordinate system. The CAD file was on a 5000,5000 coordinate system. We found two corners that were a couple of hundred feet apart and I surveyed them in. I noticed that when only the Unknown system has visibility checked on the CAD file can be viewed in the Map screen. This means that the points can be selected graphically from the Map view for localization. I localized to the two points and was then able to navigate to other corners on the site. After finding more monuments. I recomputed the localization, selecting points from the map from the imported drawing and the surveyed points.

Because of the way coordinates are handled in the database, this is an easy task for J-Field. Imported points are stored as Cartesian grid coordinates. Survey points are stored as latitude and longitude. A localization has two elements: transformation and projection. When we recompute the localization, the grid coordinates do not change, the written instructions change (the transformation) which tells the software how a grid coordinate relates to the geographic latitude and longitude coordinates. So we can recompute as often as we like without worrying about what it's doing to our coordinates.

Also, because J-Field creates nodes at endpoints of lines when linework is imported, these nodes can be selected for localization points. I've not localized a drawing before, but it worked well.

 

[Nate The Surveyor]

I want to learn this......
This is a necessary thing for me.
Yep!

 

[Shawn Billings]

Should work pretty much like I described above Nate. When you import a CAD file, J-Field creates points at the endpoints of every line. The names will be kind of strange, but it's okay. Just go with them. Be sure to import the CAD file into a Page that is setup for an unknown coordinate system. Collect your points in another page with a known coordinate system. State Plane is fine. You can pick them from the map just like any other point. You just need to uncheck (turn off) the visibility of all the Pages in known systems and check (turn on) the visibility of the unknown system. It'll work just like the localization you and I worked through last week over the phone. Populate left side with Unknown coordinate system points from the imported CAD file. Populate right side with surveyed points in known system. Watch those parameters to make sure they look reasonable. When you save the localization, give it a name that means something to you and then the Page with the Unknown coordinate system with the imported CAD file will then acquire the known coordinate system from the localization automatically. At that point, you can change the CAD page coordinate system to any system you want or change your survey page to the new local coordinate system. Your choice, and you can switch back and forth from one coordinate system to the other as needed.

By the way, the new version of J-Field should correct that small bug we found in localization when we couldn't store changes to an existing localization.

 

[Shawn Billings]

In fact, you can practice on some of those jobs that you did before and have surveyed with the LS. If you have a CAD file with points from your old system, you can import the CAD file, or make a simple one and import it into J-Field. I would recommend parsing some of the lines that you don't need out of the CAD file to reduce cluster and system resources.

 

[Matt Johnson]

You can also use Shift and Rotate for linework if you want to move a building footprint or deed polyline around in your project. I have done it and it works well. To import the drawing you can also just move the linework you want to a separate layer and then only choose that layer to be imported.