Accuracy class in the digital technical map
A number 1-5 for how precisely a network's position is known in the digital technical map (1 = centimetres). Class 9 = worse than 0.5 m or unknown.
The regional digital technical map (DTM) records for every line, pipe or other feature how precisely its position and height are known. This is expressed as an accuracy class derived from the basic mean coordinate error (position) and basic mean height error (height) under Annex 2 of Decree No. 393/2020 Coll.
How to read it
- class 1: mean error 4 cm in position, 3 cm in height,
- class 2: 8 cm and 7 cm,
- class 3: 14 cm and 12 cm,
- class 4: 26 cm and 18 cm,
- class 5: 50 cm and 35 cm,
- digit 9: accuracy does not meet even class 5 or is unknown.
Under the decree, newly acquired position and height data are kept in at least class 3. A network feature gets the worst class found at any of its points. The data are entered by the network owner, who is responsible for their correctness within these accuracy characteristics; the operator or manager may do this on the owner's behalf.
What it means for buyers
Class 9 does not mean the network does not exist. It means the actual route may differ from the map by more than half a metre, or that nobody knows the accuracy. Typically these are older water mains, sewers and lines taken over from approximate drawings. Features whose position is worse than class 3 are always kept as simplified records, because the decree treats only data with a position in at least class 3 as complete.
The mean error is an average measure of inaccuracy; a single spot may be off by more. Where the network really runs and whether it reaches a plot is stated by the network operator in a utility existence statement; before digging, the network is marked out on site.
Frequently asked questions
Is the accuracy class related to boundary accuracy in the land register?
No. The DTM accuracy class describes the position of networks and other features of the technical map. Parcel boundary quality is a separate attribute of the land register.
Can the class improve over time?
Yes. When the owner surveys the network again, for example during a repair or replacement, it enters more precise data in the map and the class changes.
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The explanation is general and informative, not legal advice. Binding are the land register, the zoning plan and other official sources.