Plat Map vs. Survey: What's the Difference?
Both documents involve property boundaries and both are recorded with the county — but they're created at different times, for different reasons, and they serve different purposes.
Side-by-side comparison
| Plat Map | Record of Survey | |
|---|---|---|
| When created | When a subdivision is first developed | After a subsequent boundary survey |
| Who creates it | Developer's surveyor | Licensed land surveyor |
| What it covers | Entire subdivision | Specific parcel(s) |
| Purpose | Establishes legal lots for development | Re-establishes or clarifies boundaries |
| Recording requirement | Required before lots can be sold | Required after certain survey work |
| Age | Can be decades old | Usually more recent |
| Found on PlatMap | Yes — all recorded plats | Yes — all recorded surveys |
What is a plat map?
A plat map is created when raw land is divided into a subdivision for development. Before a developer can sell lots, they must have a licensed surveyor draw up a plat showing every lot, its dimensions, street layout, easements, and monuments. The plat is reviewed by the county and, once approved, recorded permanently in the county records.
The plat becomes the legal foundation for every lot in that subdivision. When you buy a house and your deed says "Lot 7, Block 2, Paramount Sub No. 4," that references the recorded plat where Lot 7, Block 2 is drawn and dimensioned.
What is a Record of Survey?
A Record of Survey (ROS) is filed after a licensed surveyor performs field work to locate, establish, or re-establish property boundaries. In Idaho, surveyors are required by law to file an ROS whenever they:
- ›Set new corner monuments
- ›Find that existing monuments don't match the recorded plat
- ›Create a new parcel through a lot split or boundary adjustment
- ›Survey a parcel for which no prior survey exists
A Record of Survey often shows more detail than the original plat — updated measurements, current monument conditions, and any discrepancies found in the field.
When to use each
Buying a home and want to understand the lot
Use: Plat map
Shows original lot dimensions and easements as recorded.
Building a fence or structure near a lot line
Use: Record of Survey (if one exists) + hire a surveyor
You need current, field-verified boundary locations.
Checking for easements before landscaping
Use: Plat map
Easements are established and recorded on the original plat.
Resolving a neighbor boundary dispute
Use: Both + hire a surveyor
The ROS shows the most recent surveyed position; a new survey may be needed.
Splitting a lot or adjusting a boundary
Use: Record of Survey (result)
The surveyor will file a new ROS after completing the work.
Both are available free on PlatMap
PlatMap provides free access to both recorded plat maps and Records of Survey for Ada County, Idaho. Search by subdivision name for plats, or by ROS number for survey records.