Triangulation Software (1 Viewer)

Hi I need help. Over the summer I collected some data from radio tagged barn owls. With another researcher we collected a large amount of data. We collected a data point simultaneously (i.e at the sae time) from 2 different locations for 2 months.

With this data I am triangulating it on a map but by hand for each point. This involves using 2 compass overlays and drawing 2 lines then plotting where they cross. It is taking a long time.

Anyone know of software for a mac that can do this quicker for me?

Thanks

Not software, but a formula that might be of help if you have the national grid coordinates of your two data points.

In the olden days when I was a young land surveyor and we hadn't been exposed to computers, we had to set out and fix all of our local survey stations using a triangulation formula, seven figure logarithmic tables and a hand-cranked Facit adding machine.

If you have an electric calculator with scientific notation it should have the co-tangents (or 'cots') that you need to calculate your required location.


Consider your required point as being point 'C' on a triangle of points A, B and C (running clockwise). A & B are your known locations and the angles measured from them to Point C are 'a' and 'b'.

Here goes. I hope it's clear enough.

Eastings C = (Eastings A .cot b + Eastings B. cot a - Northings A + Northings B) / (cot a + cot b)

Northings C = ( Northings A. cot b + Northings B. cot a + Eastings A - Eastings B) / (cot a + cot b)

It's a formula I've not used since 1974, but just typing it brings back a lot of memories.

Hope it's some use to you.

Thanks,
I had a look at equations before settling on hand drawing the locations. As I have to plot the locations on a map afterwards anyway I though I might as well kill two birds with one stone (so to speak, I didn't actually hurt any owls)

I was looking for a way to quickly visualise point on a map.

I can however put that equation down as an alternative method when presenting my results.

I would look into GIS software such as ESRI.COM. You can purchase their home use version for around $100 or they have a lot of educational prices. Their software would require running a virtual windows machine or booting up in windows though.

HantaYo said:

I would look into GIS software such as ESRI.COM. You can purchase their home use version for around $100 or they have a lot of educational prices. Their software would require running a virtual windows machine or booting up in windows though.

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Thanks for the suggestion, I have sorted it now by hand. I will consider this for future use though.