Georeferencing to x y coordinates with one lat long origin?

Question

We are running parallel transect lines for a survey, which will roughly cover a rectangular area. When making the transects, we will periodically capture spatial locations of features and events we encounter.

Due to technical issues, we can only record the latitude/longitude coordinates of the very beginning of the first transect (i.e. one corner of the rectangle). The locations of all our logging of other features/events will be recorded relative to the origin, with x y coordinates (running along the east-west north-south axes, respectively).

I would like to georeference all our data points from the survey into a map, where I can click on any data point and get its coordinates in latitude and longitude.

How should I do this?

I prefer a solution that could be done in QGIS 1.7+, but ArcGIS 10 is OK, too.

Answer 1

When you say "the locations of all our logging of other features/events will be recorded relative to the origin" I assume you mean in some planarlinear measurement (lets use meters in this example). The steps you would take, assuming your data is in a spreadsheet, are as follows:

1. Project your lat/long into a local meter projection (this will depend on your location). Find the easting and northing.
2. Take your other relative measurements and add/or subtract them to the origin's easting and northing in the spreadsheet.
3. Import your spreadsheet into ArcGIS using the "Add XY data tool" (or equivalent tool in QGIS) and specify the projection you used in step 1.
4. Reproject your data into WGS84.

Answer 2

I don't know if I understand well the problem, if yes I would suggest to record the start of the transect in UTM/WGS84 instead of WGS84. This way you will record the location in meters instead of degrees.

Then you record the locations of your features/events with reference of your origin, but at this point it is easy to compute their x/y UTM coordinates as you are working in meters.

Once done it just import the spreadsheet/table in QGIS with the "add delimited text layer" tool (you need to save the table in the .CSV format) and once the points are imported give to the layer the right UTM zone and eventually save it as vector (shape, kml, etc.) with the "save as..." dialog.

Answer 3

It would be very simple to create a 'grid' of points using the python engine in ArcGIS.

You would need the start point, bounds, and increment of x and y, then simply loop along the x axis filling your points, then go to the next Y value, and loop along the x axis filling in the values, then another y value, etc, etc, etc.

I actually use this method to build a equal spaced grid of the earth:

X grid origin:        0.0000000E+00
Y grid origin:        -90.00000
X grid size:          640
Y grid size:          480
X grid resolution:    0.5625000
Y grid resolution:    0.3750000

Then looping through you can easily create a reference file for an XY layer; you just need to make sure your origin is the bottom left corner point, and then make sure the resolution is apt, and, obviously, ensure the grid size is to your requirements. All I do is make an loop of 480 (y) with the first value being -90.00000, then inside that a loop of 640 (x) with the first point being 0.00 and increment by 0.5625 for each spin through (x), then increment the first loop (y) by 0.375 on each spin through that.

The logic is quite easy really, once you know your reference points.