There are a number of factors in play here. Being a mapping guy and having a brother who is a land surveyor I probably know more about this stuff that I should :-)
One the angles called out make sure they are referencing True North or Magnetic. If it is magnetic then you need to look up the date when the original survey was done and use the magnetic declination for that time period since it does fluctuate from day to day. It's not much of a change normally but when you are talking about survey data and you are trying to close a polygon/property boundary those little differences make a hug difference if you are running a long line. The other end can be way off. Converting different coordinate systems can introduce just as many errors as well. A few inches difference here or there can move boundaries or make a property description not close as a complete polygon. Drawing on Google Earth is doing so in a weird coordinate system. Typically it is Mercator projection so that will cause the polygon to look different than it would when in a coordinate system such as state plane. Depending on the original coordinate system used the points may be called out in northing and easting which is based on a grid normally stated such as the California state plane and whatever region. Surveyors do not always reference surveys in any stated reference system, they can use their own system of grid markings and callouts. When they do this it will always be based on a physical land marker such as a pip or other type of monument. Their deed descriptions are based on that and do not necessarily tie in to latitude and longitude. So whoever may have given you that written description may have introduced additional error when they converted to lat and long. Surveyors will use a transit and rod/prism system back before the days of GPS, and even farther back they might even use a tape measure and compass. These days they can buy extremely expensive sub centimeter accuracy GPS equipment and tie their survey in to state plane or latitude and longitude. They also have ways to post process the GPS data from the field for the date and time they were measuring to a system of GPS correction files based on HARN GPS monitoring stations. As has been suggested you might want to look at QGIS and I believe there is a plugin available to type in meets and bounds descriptions to create the polygon. That then can usually be exported to Google Earth easily. Thank You, Brian Webster www.wirelessmapping.com www.Broadband-Mapping.com -----Original Message----- From: Af [mailto:[email protected]] On Behalf Of Bill Prince Sent: Sunday, November 27, 2016 2:02 PM To: [email protected] Subject: Re: [AFMUG] Converting vectors to a shape (.SHP) file? Yah. The old coordinate system is throwing me for a loop. The angle is "supposed to be" ~~ 8.3° east. However, the quarter section corners are well known, and the actual angle from the SE corner to the NE corner comes to ~~ 7.4° east. However, the easement description says 8.3° (along the boundary). So I just faithfully followed the angle called out in the easement description, and ended up 12 feet east of the actual boundary line. It can't be there, because that's not even on the same quarter section. What do surveyors do in a case like this? All the internal angles are going to end up off by about 1° too (or are they?). Crazyness. The road built on the easement has been in place for almost 50 years. A sane person would re-pin all the corners of the easement along the centerline of the road, and move on, because the description of the road/easement do not match. The errors I see between what's described in the survey documents and what is on the ground vary by between 30 and 60 feet. I'm sure part of it is because the terrain is extremely tough. Slopes of 100%, and lots of trees. I have no clue how they did the original survey in 1970. Today, you can GPS almost any point you want/need. bp <part15sbs{at}gmail{dot}com> On 11/27/2016 10:49 AM, Chuck McCown wrote: > Oh, OK, yeah, totally forget geocodes when doing metes and bounds. > All the datum conversions etc prove to be worthless when trying to be > very precise. > And most section lines are not true NWES and most section lines are > not one mile either. Sometimes you luck out with an exact mile lying > on one of the ordinate directions but that is infrequent. > > You have to use physical monuments and the DMS lines of the metes and > bounds. Frequently they are in that old "N 12 deg 3 min 2 sec E" format. > I just go through and convert all the angles to Cartesian angles > first and then start laying down lines in the drafting program. Or in > google earth. You can describe a line/path with a bearing and distance > in GE. > > -----Original Message----- From: Bill Prince > Sent: Sunday, November 27, 2016 11:35 AM > To: [email protected] > Subject: Re: [AFMUG] Converting vectors to a shape (.SHP) file? > > The easement starts at the eastern boundary of the quarter section > (which is not true north south; a little over 8° east). According to > the description it is supposed to be on that line at a certain > distance from the corner. > > When I drew it on GE, I just measured that distance on that line, and > it actually comes out 35' north of where the road actually got laid. > No big deal, the easement is 60' wide, so it mostly fits. > > However, when I used this tool to get a lat/lon, the point is about 12' > to the east of the point I measured. Now I know that drawing something > like this in GE is somewhat error prone, but I did not expect it to be > this far off. > > bp > <part15sbs{at}gmail{dot}com> > > On 11/27/2016 10:28 AM, Chuck McCown wrote: >> The easements I do are totally desk top, no survey. But I do have the >> recorded metes and bounds of the property to go by and generally use >> its boundary. But my point is, easements are generally a lot more >> loose than a property description used on a deed. I am not surprised >> that you may find a significant error. After all, the easement was >> just to get the landowner to allow something to be put there. If it >> is a public utility company and it gets contested they will just file >> a quiet title action and get it corrected due to having the right of >> eminent domain. >> >> Have you compared the metes and bounds of the easement with the >> parcel boundaries or is it just heading cross country through the >> middle of a parcel? >> >> -----Original Message----- From: Bill Prince >> Sent: Sunday, November 27, 2016 11:17 AM >> To: [email protected] >> Subject: Re: [AFMUG] Converting vectors to a shape (.SHP) file? >> >> This is actually for an easement, and it's open on both ends. It does >> start at the corner of a quarter section, but from there it's just a >> zig-zag line. Internal coordinates are unknown. >> >> To make it more complicated, the original coordinates are based on >> the "California Coordinate System, zone III", which was derived using NAD27. >> So I had to convert those CCS-zone III, to NAD27 (lat/lon), then to >> NAD83 (lat/lon), and then to WGS84 to get something close to >> something I can use with GE. >> >> I did convert the first vector, and it appears to be off by about 12'. >> Something stinks... >> >> >> bp >> <part15sbs{at}gmail{dot}com> >> >> On 11/27/2016 10:01 AM, Chuck McCown wrote: >>> I do this on a regular basis for easement work. There is a nice >>> range/township/section overlay you can buy for GE so you can at >>> least find the section corners. Most metes and bounds use a section >>> corner or a quarter corner as the point of beginning. If a parcel is >>> complex, I actually lay it out in solidworks, my 3D mechanical >>> design program, that way I can just directly enter the angle >>> directions and distances. And the parcel almost always closes. You >>> could do that with any drafting program most likely. >>> >>> Then I export that to an image and import the image into GE. Stretch >>> and rotate to fit the visible landmarks and monuments. >>> >>> There will always be an error in closing unless they wind up with a >>> "more or less" to point of beginning. That takes all the slop out. >>> >>> -----Original Message----- From: Bill Prince >>> Sent: Sunday, November 27, 2016 10:49 AM >>> To: [email protected] >>> Subject: Re: [AFMUG] Converting vectors to a shape (.SHP) file? >>> >>> The vectors describe a property line, and start at a fixed WGS84 >>> coordinate. Then it's a series of distances and azimuths from there. >>> I tried drawing them with GE, but there is an accumulation of small >>> errors. There are about 10 vectors total. >>> >>> Something like starting at point lat/lon, go 700 feet azimuth 8° 27' >>> 42", then 200 feet azimuth 27° 15' 08", and so on. >>> >>> >>> bp >>> <part15sbs{at}gmail{dot}com> >>> >>> On 11/27/2016 9:13 AM, Chuck McCown wrote: >>>> Is the end result displaying your vectors on GE? If so there are >>>> ways to just import them as a text file. >>>> I did it, don't recall how, perhaps I used some kind of app but in >>>> the end, it was easy. I may have just drawn a line and then >>>> reverse engineered the KMZ or KML file. >>>> >>>> -----Original Message----- From: Bill Prince >>>> Sent: Sunday, November 27, 2016 8:58 AM >>>> To: Motorola III >>>> Subject: [AFMUG] Converting vectors to a shape (.SHP) file? >>>> >>>> >>>> I have a boundary between parcels that is described as a series of >>>> vectors (distance & bearing) from one point. Apparently this can be >>>> imported into Google earth as a shape file (.SHP extension). I have >>>> been looking for, but not finding a tool that allows me to enter >>>> the vectors in text, and spit out the .SHP file. Does anyone know >>>> where I might find this? >>>> >>>> >>> >> >
