Plotting points that have relative coordinates rather than total station coordinates on map?

Question

I have about +100 points of various descriptions from an archaeological survey. They are the backlog from years of excavations BEFORE systematically using Total Station at the site. For each artifact I have the upper and lower elevation data, in addition to the distance from either the NE, SE, SW, or NW point of the grid square. The location was recorded using two meter tapes from two points intersecting at the point of the artifact. The Excel file I have records the grid corner point and the distance from that corner to the artifact (ID1 and Radius1, ID2 and Radius2).

First, I need a method that will help me systematically upload the points. How do I arrange my Excel file, and what do I do in QGIS to get it plotted properly?

Second, I want to be able to answer questions of spatial relations based on elevations.Is there something special that I need to do for the input of the data in the .csv file?

I'm new to QGIS.

Answer 1

Your problem looks like a bilateration issue.

This way it works for me:

We start of with the corner coodinates in a projected CRS (here: EPSG:31466):

file corners.csv

corner,E,N
A,2530114,5725986
B,2530338,5726216
C,2530525,5726401
D,2530655,5726370
E,2530917,5726264
F,2531381,5725999
G,2531197,5725785
H,2530698,5725334

and the points and measured distances, one line for every distance and two for every point:

file pointdist.csv

point,corner,dist
1,A,146
1,B,211
2,B,134
2,C,158
3,A,369
3,H,516
4,A,425
4,B,303
5,D,192
5,E,120
6,G,203
6,H,563
7,H,125
7,G,586
8,E,216
8,F,462
9,F,163
9,G,166

Load corners.csv and pointdist.csv with Add Vector Layer

Rightclick on the pointdist layer Properties->Joins

Join layer: corners
Join field corner
Target field: corner
Save As... pointcornerdist.csv

Load pointcornerdist.csv as Delimited text and EPSG:31466

remove the other two csv layers

Rightclick -> Set Project CRS from Layer

Settings->Snapping options: pointcornerdist.csv 10 pixels

Create a New Shapefile Layer of type polygon EPSG:31466 name site.shp

Draw a polygon along the corner points

Rightclick on the polygon layer -> Properties->Style: Simple fill : No brush

Vector->Geoprocessing->Buffer(s)

Input vector layer: pointcornerdist
Segments: 20
Buffer distance field: dist
Output shapefile: buffers.shp
x Add result to canvas with EPSG:31466
Close

Vector->Geometry Tools -> Polygons to lines

Input Vector layer: buffers
Outpt shapefile: bufferlines.shp
x Add result to canvas with EPSG:31466
Close

Remove layer buffers

Vector->Analysis Tools-> Line intersections

Input line layer = Intersect line layer: bufferlines
Input unique ID field = Intersect unique ID fiels: point
Output Shapefile: intersect.shp
x Add result to canvas with EPSG:31466
Close

Rightclick on intersect.shp -> Filter

Click on point_1 = and point_2

Vector->Geoprocessing Tools -> Clip

 Input vector layer: intersect
 Clip layer: site
 Output shapefile: points.shp
 x Add result to canvas with EPSG:31466
 Close

Re-Add corners.csv, this time as Delimited text and EPSG:31466

label points layer with point_1, and corners layer with corner

and you are done: