Still Struggling With Localize

I seem to have a mental block when it comes to implementing the localize procedure. I tried again today, but failed to get it to work. Here's what I did, near as I can recall:

1. In the office I created rough (within a foot or two) search locations for the desired points by laying map linework over a georeferenced image and assigning CAD points to the desired map locations.

2. I exported the CAD points to an ASCII file. The points were assigned elevations of zero, so only the N and E were valid (within a foot or two).

3. In the T-LS I created a CONTROL page with NAD83 SPC as the coordinate system, and a SEARCH page, also NAD83 SPC.

4. I imported the ASCII file into the SEARCH page as design points.

5. In the field I located 2 of the monuments that correspond to 2 of the search points.

6. On the Localize screen I linked the 2 surveyed points with their corresponding search points, holding N and E only. The resulting N shift was about 0.7', the E shift about 0.3', rotation about 0°08', and ppm about 39. These points are about a half mile apart, so I figured that was a reasonable match.

7. On the SEARCH page I changed the coordinate system from NAD83 SPC to the system created on the Localize screen.

8. I staked out one of the design points and it was around 2 feet from the monument, at which point I acknowledged my localization-resistance and gave up.

I have a couple of cheat sheets that I ratholed some time ago, one is Duane Frymire's and the other I put together myself, though without a lot of confidence in it. I note that both of them suggest that the points have to be imported to a page that already has a custom coordinate system assigned, but I'm not sure that's a requirement. Duane's further directs the user to restart the base after localizing, which seems like a major inconvenience that I hope isn't necessary. I'd really like to just locate a couple (or more) points, localize on the spot, and continue searching for more without having to return to the base.

A few of the 5PLS guys have kindly walked me through this before, and I hesitate to ask again because I hate looking stupid, but I'd really like to document a bulletproof process that I can follow in the future in order to put what I know to be a very useful procedure in my personal toolbox.

Thanks to anyone willing to assist!

You can not import your local coordinates as State Plane Coordinates. They aren't State Plane Coordinates, they're local. So before importing the coordinates, create a local coordinate system with the underlying system being SPCS.

If you do what you describe, importing local points as SPCS, you can correct it by developing your localization and then re-importing the points, this time using the local system. But it's best to start on the right foot and import them as local coordinates in a local coordinate system.

Coordinates that are imported as SPCS are treated as SPCS. Switching coordinate systems only reprojects them, but does not transform them.

This video I made in 2017 covers that, as well as some other common issues that can occur with localizations.

Jim Frame said:

I'd really like to document a bulletproof process that I can follow in the future in order to put what I know to be a very useful procedure in my personal toolbox.

Click to expand...

Localizations are covered in the User’s Guide on page 112. Notice that the red font highlights the mistake you made.

Jim, as above you do have to create a custom coordinate system. The house icon creates local one. No longer necessary to re-start, might have been some other changes since that cheat sheet (I don't use the routine much either). Shawn's video is excellent! Should be reviewed by anyone using this procedure.

Shawn Billings said:

Coordinates that are imported as SPCS are treated as SPCS. Switching coordinate systems only reprojects them, but does not transform them.

Click to expand...

It looks like my fatal error was not setting the SEARCH page to a local system *before* importing the points. I'll add that to my procedure list and try again next project.

Thanks, all!

Took me a while to get it also. Just make the local system, before you import anything into the unit, and you should be good to go.

Yeah, Jim. Just what James said. Setting up the local system before importing has worked for me every time. Once I learned that I have been good to go ever since.

I gave it another go today, but still appear to have something bollixed up.

I started a new job, created a new page (SEARCH) with a local coordinate system, then uploaded my search coordinates to the SEARCH page. In the field I located 7 points and, in the localization screen, matched them up with their design points (NE only, I don't know anything about the elevations yet). After saving the localization, and while still set up on the last point located, I staked out the design point and missed by 1.6 feet or so.

I'm hoping that a few screenshots will disclose whatever I'm doing wrong:

The one thing that stands out to me is your surveyed coordinate system is WGS84 and not state plane. If your surveyed points were located on state plane the the survey tab needs to say which state plane system you are in.

Matthew D. Sibole said:

The one thing that stands out to me is your surveyed coordinate system is WGS84 and not state plane. If your surveyed points were located on state plane the the survey tab needs to say which state plane system you are in.

Click to expand...

I don't think that matters in localization. I don't see anything that looks like it would cause an issue. Instead of shakeout see what inverse looks like...

Are you working with the local "search" page set to current?

Adam said:

Are you working with the local "search" page set to current?

Click to expand...

I tried it both ways, got the same results.

Shawn Billings said:

see what inverse looks like.

Click to expand...

The inverses all look good, within a few hundredths. (Before editing this post I had said that there was a shift, but that was a goof on my part.) So what did I mess up to make the stakeout tell me to move 1.6'?

It seems to me like I had this trouble before. A wild guess is I think you should be locating the control in the same page as the search page. I do not use this much but that stands out to me...

You stated at first you located the control on a page in SPC the changed to search page to localize, I almost swear I did the same thing before and had a similar shift issue.

Sdrake14 said:

You stated at first you located the control on a page in SPC the changed to search page to localize

Click to expand...

That's what I did. It seemed to me that I should keep the control (real-world coordinates) separate from the design coordinates.

Jim Frame said:

I tried it both ways, got the same results.

Click to expand...

Yes this does not matter. Only the design points have to be imported into a local coordinate system. The current coordinate system and page do not matter when surveying points as points are always stored in the database with WGS84 coordinates. I would need to see the project to find what might be wrong.

The project archive can be found here if anyone wants to take a look.

Hi Jim,
1. I verified the localization. It works fine by itself. I would suggest to use underlying SPCS system if you know it. It reduces projection distortion especially for wide spread projects. But it is not related to your issue.
2. It is not clear for me what goal for that workflow, when initially you use “rough (within a foot or two) search locations for the desired points“ as actual design points. Usually localization is used for creating or tuning coordinate system by given known design coordinates.
3. If you need just to find points you can use alternative method, that is not creating new system, but moving base instead, to match surveyed point to target coordinates. It is M-Local. So please import coordinates as NAD83 SPC. Survey one or few points and match them to imported ones. After that all further collected points with that base will live in shifted system. So you can stake out them.
4. We will try to reproduce the issue in our local Moscow system for better understanding why stakeout behaves that way. When I localized by using SPCS underling system I saw localization shift around 1.15 feet, that very close to the stakeout error you saw.





I hope we solve that puzzle soon together.
Best regards,
Vladimir