Fixed Points from Survey

Question

Aloha! I am hoping to get some advice on introducing fixed points into our about-to-be-deployed, newly upgraded ArcGIS Pro Parcel Fabric (currently v5, Enterprise 10.9.1, ArcGIS Pro 2.9.x or may be 3.1.x.

We have contracted with Eagleview for another cycle of imagery capture that will include Certified Orthomosaic and True-Touch technology. Particularly important to note here is that Eagleview will identify visible 'targets' (landmarks) that a surveyor will collect survey grade coordinates in order for the orthomosaic to be spatially aligned accurately.

Now for my question:

I am attempting to convince the survey coordinator (Sr. Management) that it is important for us to align our Parcel Geometries with the imagery on delivery, and in order to do that Coordinates that we can use for LSA would be useful. Typically, Eagleview utilizes items such as sidewalk curbs which will not help us at all. I have identified visible cul-de-sac centerpoint monuments throughout the County that I am more than willing to create a more visible target for them (example below) for these as they will need to do this in parts of the County where there are no cul-de-sacs and they would prefer to minimize the number of times that will be necessary.

What other types of parcel-related landmarks could we use? Obviously, a random concrete pad or large rock or whatever it is they choose will not allow us to use those as fixed points for adjustment.

Side note: The County does not require surveys to contain coordinates when submitted for approval. As a result, NGS monuments are our only 'fixed points' and we have not historically made any LSA and simply visually aligned with previous imagery to the best of our ability.

Thank you in advance for any assistance.

ElisseDeleissegues1 · Answer

Aloha Tim, thank you for your reply.

We had attempted to use NGS point references as as POB from the documents in ArcMap PF, and it wasn't terribly accurate over time. Part of the reason is that for each imagery delivery there are 'shifts' in the delivery; by which I mean that with each new mosaic the appearance of the image for each tile was slightly different that the last version making it appear that the POB destination wasn't aligned correctly (one), and there are what we have somewhat affectionately called 'schizms' that are located in different places with each delivery (two-see attached example).

We are intending to attempt the method you have described above and hope that helps in conjunction with the certified orthomosaic and True-Touch upgrade.

Yes, indeed, I have sent a dataset of visible cul-de-sac physical markers as of our last delivery and intend to strongly encourage them to use as many as possible. I had suggested parcel corners in areas that do not have cul-de-sacs, of which there are many, however they are suggesting that we would need to hire a surveyor ourselves (which is not going to happen especially this cycle) and we are unfortunately on a bit of a time constraint. As of now, the choices they make for their targets will be sent back for approval before beginning.

I'm interested in if anyone else has suggestions on any other alternate possible landmarks that we could use to tie in our parcels with the imagery in a pinch.

It's curious to me that this sort of request has not been suggested to Eagleview previously as they seem quite puzzled at my request.

TimHodson · Answer

Hi @ElisseDeleissegues1 ,

To your question and reference to use of the NGS point. I know you are asking for other methods, but I'm curious about how you are currently using the NGS point reference, if at all? The reason I ask is that last year and earlier this year a few of us on the parcel development team had the opportunity to review a large number of land records documents from in and around Honolulu.

We noticed that the NGS point reference used for the point of beginning appears on most (pretty much all?) of the documents.

I see this same NGS-reference pattern on the document you've shared. Based on our research we found that NGS references are valuable for geolocating parcels with better than expected positional accuracy. It requires the use of feature templates that use geodetic azimuths, as described here:

https://pro.arcgis.com/en/pro-app/latest/help/data/parcel-editing/use-geodetic-directions.htm

I will follow up with additional information on this method.

Regarding the painted locations for the centers of cul-de-sacs. The painted /surveyed locations used for the photo-control could serve double-duty as a tie-in to the parcel boundaries if there is a physical marker in the asphalt (iron pipe or similar) that can be positively identified as the "true" (in parcel boundary sense) center of the cul-de-sac, and that is what gets painted/surveyed.

-Tim