May 09 2011

We have no clue where this data came from…

How many times has this happened to you: you receive a dataset from a client or a prime on a project and it has no defined projection or metadata information. We work with anyone from the federal government level  to private bridge designers and we’ve seen it over and over again, especially with client provided imagery.

Defining a Coordinate System for an Undefined Dataset

1. What is your project coordinate system? Have you defined it? This is important! Are you working in survey feet? We’ve seen many engineering projects steamroll right past this question and then get all tangled up. Try to define this right at the very beginning in your scope of work.

2. Go to the source of the data. Contact the client or who you received the data from and ask them what the coordinate system. This may seem obvious but it’s very easy to waste too much time trying to figure out what the system is before simply asking the entity you received it from.

3. Download the image of the known project area through USA Photomaps. Pull your downloaded image and the undefined dataset into your software package and compare within potential coordinate systems. Use Corpscon to convert an individual point location if needed.

4. Is it a feet versus meters issue? Survey feet versus feet? Pay attention to the survey feet question and examine your data closely. Sometimes it’s only 10-15 feet shift but you won’t notice unless you zoom in.

5. If you see a location that is less than 10,000 x 10,000, it is 99% likely in a local system.

6. Be aware of a modified state plane system especially if the data set appears to just be off by a symmetrical shift.

These tips may seem simple but these questions come up often! I cannot emphasize enough how important it is to define your working coordinate system at the beginning of your project!

Has this happened to you? What is the core software package that you work within?

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