"base" coordinates keep randomly changing
Here is what I have on the Transformation tab,
Putting your drawing in the appropriate State Plane is admirable. If your xrefs are referenced to the correct State Plane then those xrefs should be correctly positioned relative to 1) your basemap, 2) relative to the other attached xrefs, and 3) relative to Bing Satellite Maps. This is true because they are all referenced to the same 0,0 point (which was determined by the correct Zone in the correct State Plane).
To test, first open a clean, fresh drawing using an out-of-the-box imperial or metric template. Second, assign your State Plane CS with the correct Zone. Third, attach your xrefs one-at-a-time, insertion point=0,0, scale=1.0, and rotation=0 degrees. Fourth and finally, turn on Bing aerial imagery and everything should be in harmony. If not, then you have issues.
Notes:
The most common reasons for inconsistent positioning of line work are, but not limited to: incorrect coordinates assigned to modelspace, incorrect CS used when drawing the xref or the basemap, UCS orientation not set to 'world,' C3D/M3D considers the CS as 'unknown' (such as when using a site specific or local datum), insertion scale errors (inches vs feet vs meters vs millimeters), and the original author falsely claiming his drawing was correctly georeferenced, when in fact, it was not.
Chicagolooper
No, being far away from 0,0 point, or the origin, is not the issue. All State Planes have coordinate values in the one-hundred thousandths as well as greater than 1 million. No matter the State Plane, with US Survey feet as the units, you will not find neither x- nor y-coordinate below 100,000. That is the nature of State Plane.
- What does 'Derived from the same source drawing' mean? Who is the author? Your full disclosure will determine whether you really want to solve this.
- What is the State Plane and Zone for your xrefs? E.g. Ohio has 2 zones, north and south. Indiana has 2 zones, east and west. Texas has 5 zones. California has 6 zones. Alaska has 9 zones. States like Tennessee, North Carolina, and New Jersey have only one zone which covers their respective State.
- What is the coordinate system you have assigned to modelspace?
The origin is not moving. If it is, then you have successfully undermined AutoCAD and the industries that use AutoCAD.
Chicagolooper
Great, we are making progress. You need to good to the folder with the shapefile. Double click on the .prj file so it opens in Notepad, then take a screenshot of the contents.
Then next thing will be to check your work flow to 'bring in' the shapefile. Are you using an FDO connection to bring in map features? Or are you using MAPIMPORT to convert the shapefile into Cad entities? But before anything else, need screenshot of the prj.
Chicagolooper
Accepted solution
OK. You are doing work for the DOT or a similar agency. Do what you're doing, or what you did, but this time don't use your Department's standard issue template. Open a fresh clean drawing using No template-Imperial.
You want to use No Template then attach your xrefs because DOT templates are notorious for having settings 'built-in' and these settings can adversely affect your line work when you insert or attach Cad entities. By using No Template you 'liberate' yourself from those settings.
Also, is it possible to verify whether the GIS data is using California State Plane, NAD83, Zone 3, US feet and not something else, like WGS84 Lat/Long degrees or UTM-meters?
You have also assigned CA83-III US feet to modelspace and I assume it is the correct CS. Your 'input' CS can be anything appropriate given the xref's location, the input CS dorsn't have to be the same as the resultant CS in modelspace-Cad will perform the required transformation between input and resultant. As long as the input and resultant CS's are appropriate and are in the Cad coordinate system library, the transformation will be successful.
Chicagolooper