Do I need a surveyor to map things in my community?
The long answer involves lots of caveats and what-if-but-then-again scenarios, with underlying theory and math related to spherical projection models and datums. However, it isn’t important in our context of online mapping and municipal geospatial data.
The short answer is “no” and “yes.” Here’s how to approach this issue:
Consider your purpose and stick to it
The overall purpose of your municipal geospatial data is to provide reference-level information to your community and to provide management-level information to your municipal users. We discussed this in our last blog post. To achieve the relative on-screen accuracy that is sufficient, you can start placing pins and tracing areas from publicly available aerial photography.
When you create your sufficient data for mailbox locations (or the project of your choice) make sure to document when you did it and how you did it. You don’t need to be hung up today on whether or not you’ve created the perfect data suitable for every future use. By recording “metadata” about your current purpose, you’ll be able to provide disclaimers and reminders to other users or agencies in the future about the accuracy and precision of your data. Whatever you have done will likely be a good jumping off point for someone else in the future. Other, future, users can choose to use it as-is or refine it based on their purpose at that time.
But sometimes, the short answer is “yes.”
Within your municipal GIS, there are likely to be certain types of information that do require high precision and accuracy. An example might be modeling flows within a sanitary sewer system for capacity planning. For that type of project, you need to engage licensed professionals and the location of infrastructure should be collected by registered land surveyors.
Rules of thumb
- If you can see it on an aerial photo and “good enough” is acceptable, start tracing!
- Anything that needs to be located within 6 feet horizontal accuracy should be done on-site using field-grade equipment. Your own staff can do this type of work. You can find some great products for under $2,500 at Stakemill or rent equipment for short-term projects locally.
- Anything that needs to be located closer than 3 feet horizontal accuracy should be done with survey-grade equipment by manufacturer-trained staff. You can still do this using your own staff, but the equipment costs and time commitment are higher.
Anything that requires elevation information or horizontal accuracy closer than 1 foot should be done by a registered land surveyor.