Following some recent threads on GIS and finding data sheets for city survey monuments, I decided to revisit GIS and see what I could learn. Don't be too critical; this is the result of about 5 days, off and on, work.
This map portion is in QGIS. I downloaded the open source software, used some internet searches and some old shapefile data I had developed earlier in DNRGPS.
What it shows is a portion of the completed part of three NCDOT projects in Guilford County, NC. The base map that shows roads is a Tiger file from the Census Bureau. The BL points are from a public NCDOT project file, converted from text to .shp in DNRGPS. There are two NGS marks which appear in red. The basemap, the BL points, and the NGS points are each in separate layers.
There's a lot left to learn. The basemap system is EPSG:4269 while the other two layers are in EPSG:2264. The coordinates for the NGS marks are a couple of feet different from the NGS datasheets and there's some question in my mind about the ellipsoid(s) used. While the map looks good, plane coordinates taken from it would not be advisable.
So, with some minimal background, enough details can be figured out to produce a reasonably representative map. The BL points generally follow the completed road and the project begin and end points (near the Guilford College Road intersection) are in the right area. Inexperience and sketchy knowledge, though, are not a good combination for exact work and that's where the danger lies.
Pretty good entertainment for a math nerd, but real work needs to be in better hands.
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The green points are a download of a shp file from NGS for a few not-so-carefully selected marks near the project. I had never even thought about downloading monument shapefiles, but it's kind of nice to have them on a local map. They're in a separate layer.
I suspect that the learning curve gets steeper, but this early part is pretty easy, probably even easier for folks with CAD experience.
It's black box, though, in a lot of ways. You really have to be careful with the metadata associated with each layer; easy to see how gross errors can occur.
QGIS is a great tool and is well supported by its user community.
qgistutorials.com/en/ provides a good set of tutorials, enough to get someone started.?ÿ There are many YouTube videos available as well.
Each November I make a donation to the QGIS.org Association.
GB
It becomes somewhat intuitive once you get going. The supporting data that comes from NGS with a shapefile is helpful.
There's certainly value here.
