Here's a specific dumb question: I have the coordinates of the county monuments as shown at bottom, and I have the parcel map, attached. But how do I get the grid coordinates of a property corner? I've highlighted in yellow example dimensions given on a prior map. If I wanted to check the numbers in yellow, how is it done? In other words, how would I plot monument locations on a parcel map?
1.) Enter the grid coords for points BR-4,5,6 into a traverse program and inverse between the points for the bearings and distances.
2.) Check the inverses against the map and see that the map is on ground datum and the traverse program is on grid datum.
3.) Convert any map distances you want to use to grid datum = map.distance x 0.9999298 per the Precise Traverse Sheet.
4.) Traverse 98.29' to the RR.SPIKE and then 20.299' (6.187m) to the NW.PL.CORNER.
5.) Traverse 16.68' (5.084m) to the NE.PL.CORNER.
6.) To continue traversing grid coords be sure to convert all map distances to grid distances and close the traverse back to where you started.
The coordinate calculation sheet was from 1968. The survey plat is 1996. Are you wanting to use NAD27 coordinate values?
Thank you, especially to Landbutcher464MHz for your sketch which demonstrates impressive bandwidth! However, my question is different.
Suppose all I have are the county monument locations, and the parcel map. The county monument records don't reference any property corners. And the parcel map doesn't reference any position (such as geodetic or grid), it only specifies bearing and relative locations. I want to make a map of the parcel and the county monuments. Where can I find the position of any parcel corners relative to the earth, either geodetic or SPC? In other words, if I were to pinpoint the location of the county monuments on the parcel map, how would I know where to place them?
@bernardc This question has a very simple answer to a not so simple question. If you have a parcel map, which is essentially a GIS cartoon, and you wish to establish the location of those lines in relation to published coordinate values on specific county monuments such that they can be related to each other, if they are in the same datum and projection, you can combine them to get you into the ballpark, but at that point, you would need to do an actual survey to establish the true nature of their relationship by tieing down both the county monuments and the propert corners that represent the location of the GIS lines on the ground. Every single situation is going to be slightly different and require a modified approach. Such is the nature of surveying, there is rarely ever a cookbook recipe to follow but is determined by the circumstances and nature of the available data to be used to get started.
Just because I'm paranoid, doesn't mean they aren't out to get me.
@williwaw Thank you. I'm gradually converging on the right way to pose the question.
I must be missing some information from the parcel map, because it would be a GIS cartoon if it had any reference to a geodetic location in any form, but it doesn't. Does it? The way I'm reading it, the quantitative information on the parcel map makes no reference to where on the globe any point on it is located. Other than geographic words like "California," this map could depict an area in Spain.
Like @williwaw said " you would need to do an actual survey to establish the true nature of their relationship by tying down both the county monuments and the property corners that represent the location of the GIS lines on the ground". In other words you need a surveyor to do some field ties to get the coordinates accurately that you want.
Another rough option (+/- 15 feet) would be to find your job on Google Earth and pick a fence corner or some other identifiable point that might be one of your property corners and read the UTM coordinates. Then calculate a traverse around your map starting with that coord.
Okay while I was writing you posted a map that I ignored earlier. That is an assessor map showing all the available survey maps in your Contra Costa County, definitely not Spain. You need to request some of the survey maps shown around your particular lot or parcel. Those survey maps will have much better data and possibly some ties to control like your example map.
This is a tough nut to crack. Let me take another try at it by narrowing it down to two questions, neither of which pertains to any new measurements:
- Does a parcel map provide any quantitative geodetic position coordinates, either directly or in a mathematically related coordinate system?
- @williwaw writes, "you can combine them." I could if I had at least one point on the parcel map with a coordinate related to any known coordinate system, but I don't think I have that. Do I?
@bernardc Do you have a static pdf/image out of this GIS or are you in an AutoCAD/GIS environment? If it’s just an image, not directly helpful but if it’s a GIS/CAD program/file, yes, you can assign coordinates to linework in whatever datum/projection it’s set up in. You can manually drop coordinates on your county control points into that CAD environment assuming datum/ projection/units et al., and if they plot in what appears to be a reasonable location, the next step is put that information into your survey software and go out and play hide and seek. Your question is so lacking in specifics that’s nearly impossible to answer. With what you’ve provided there are myriad possibilities.
Just because I'm paranoid, doesn't mean they aren't out to get me.
@williwaw This question is as slippery as an eel. But allow me to try to grapple with it.
I'd have no trouble drafting the parcel map data, checking closure, and distributing the errors. But how would I assign coordinates? "How" in terms of knowing what numbers to assign. Let me ask a specific question:
What are the CCS83 Zone 3 coordinates of the point at this red arrow on the previously attached parcel map:
@bernardc What I typically do is go to some source which could be one of many, a GIS, another previously done survey done in the area using the defined projection or even Google Earth and try and determine as close as I can, either a coordinate in that projection or a decent lat/long and use the projection parameter to convert it to a grid coordinate. Then go out and use those coordinates to get close enough to find evidence, record property corners that are identified in the original description, as well as the county monuments you referenced. Once I’ve found and tied them both, I now know exactly how they relate and my original best guess search coordinates can be ignored or compared to see ‘how close’ they got me. That’s it. There’s no shortcut. If you find one let me know.
Just because I'm paranoid, doesn't mean they aren't out to get me.
What are the CCS83 Zone 3 coordinates of the point at this red arrow on the previously attached parcel map:
This is not a Parcel Map that you are looking at. This is an Assessor parcel map used as a reference map showing possibly all the survey grade Parcel Maps & LSMaps that have been recorded and are available to be ordered. If you were to order those PM and LSM maps that are listed near your red arrow you might find the coordinates or ties to other coordinates that will let you calculate CC83 Zone 3 coordinates for that red arrow point. I have done this many times and after actually measuring the point with survey grade equipment, I have found the calculated coordinates to vary between hot +/-0.10' to terrible +/-3' so it's not a sure thing.
If the survey map thing does not yield any coordinates then the advise from @williwaw is your only other option.
Either way, to get accurate reliable CC83 coordinates you need to do some surveying unless you find a MAP like 7529 with accurate traverse coordinates like you posted above.
The way to do it is thus: Go to the field and survey the points with either instruments tied to a known Geographic point or with GPS.
If you want to just get close, look on a resource such as Google Earth and pick possible coordinates on the photo that match your parcel such as fence corners. That can get you in the ballpark, maybe within 10' or so.
I feel like Inspector Clouseau. "Now we're getting somewhere."
I did research the maps of that corner and another one. Both trace back to monuments set in 1914. So their geodetic or grid coordinates can only be based on field data, not synthetic calculation. I made a little graphic to show the chain of references.
I'm curious about the calculated coordinates @landbutcher464mhz mentioned that lands between a tenth and 3' of the measured point. What is the raw data for those calculations?
Those plats are from 1982 and earlier. There isn't any chance they would have an NAD83 coordinate shown. If they did show a coordinate it would be an NAD27 one. I don't see any. If it did you can do an estimate conversion that would get you kinda close to a modern day coordinate. This is a bit like showing a picture of a random person with nothing around them in the picture and wanting to know how tall they are and what they weigh.