UPD data sources

From Wikicap - European Commission

Go up to the main update page

To make the update meaningful, it is necessary to assess all source data to verify that they are both current and suitable for processing the change. Even though many different data can be used as input, the process relies most of all on using of aerial or satellite imagery.

The usefulness of this process relies on the simple condition that the potential data sources can be discovered (the operator be aware of their presence). In ideal cases, catalogues and geoportals within the national/regional SDI are available that provide metadata records about the quality, currency, and accessibility of the available data. If no SDI has been put in place, the necessary information has to be collected and integrated in the LPIS itself.

The process should guarantee that the selected data must be interoperable with LPIS (reference system, resolution, scale, quality, etc).

A number of reported anomalies are based on observations from other data sources, rather than imagery. They may carry attributes values of the reference parcel with or without geospatial component:

  • An OTSC inspector can provide a valid reference area value.
  • A part of the boundary can originate from topographic surveys.
  • An appropriate "as built" plan can be delivered from a third party partner.

Depending on the particular conditions, such data from non-image sources might be more appropriate than the most recent image. This is especially the case when such data is more current than imagery.

The workflow of assessing and categorising potential data sources is illustrated with the following activity diagram Figure 6.


Figure 4: Workflow of assessing and categorising the potential data sources

The assessment process involves:

  1. Start the assessment by retrieving an open anomaly; each anomaly informs what the problem is and so sheds some light on what data might be necessary for processing.
  2. Check the source data availability (image, RP boundary geometries, RP area). This yields an initial decision about availability of data based on the metadata and preview of the source data. Availability involves existence, specifications as well as access.
  3. Make a more detailed analysis whether the quality of the available source data is fit for resolving the anomaly. This involves
    • Checking its completeness: the whole area of the reference parcels concerned by the anomaly should be covered by the same imagery. Likewise, other third party data (transport, hydrology, etc.) have to support all parcels that are related to the anomaly in question. If the data isn’t complete, it can be still used, but only as ancillary data (additional data supporting decisions).
    • Checking its currency: older imagery may not reflect the most recent state of the land, but, if no manifest change occurred, the multi-temporal dimension still provide valuable clues of the nature of that land.
  4. If suitable source data has been found, it should be used without delay for further anomaly processing,
  5. If no suitable sources data, but only ancillary data have been identified, it should be recorded and the processing of the anomaly should be postponed until sources become available. Document the anomaly appropriately.

Go up to the main update page