Method & data sources
Vilac GIS estimates reference land prices from the Lâm Đồng land price table in force since 1 January 2026 (Resolution 82/2025/NQ-HĐND) and market asking prices, adjusted for position, access road, plot size and land type. In cross-validation on 271 samples the median absolute percentage error was 42.1%, so results are reference levels, not sale prices or a certified valuation report.
Estimation method
Reference prices are built from market price samples with a known location, land type and date; they are compared with the state land price table and adjusted for position, access road, plot size, shape, terrain and the available legal information.
Asking and sale prices are kept apart where the source allows. Unusual or incomplete samples may be dropped or down-weighted. Results show the reference level of the available data, not the sale price of a particular plot.
Main data sources
- Lâm Đồng land price table: Resolution 82/2025/NQ-HĐND issuing the land price table in force in the province from 1 January 2026. Lâm Đồng Provincial Official Gazette.
- Market data: asking-price samples and transaction information, grouped by area, land type, source and date. Asking prices can differ from actual sale prices.
- Minerals: Decision 866/QĐ-TTg approving the 2021–2030 mineral plan with a vision to 2050; the layer is used as a lookup warning. Boundaries must be checked against the records and with the competent authority.
- Base map: OpenStreetMap, data under the Open Database License (ODbL), credited to its mapping community. OSM copyright and licence.
- Elevation, slope and access roads: digital terrain and road data vary by area; used only where the layer exists and meets quality checks.
Validation and confidence
The model is reviewed regularly against price samples held out from calibration, with errors checked by area and land type and large deviations reviewed. Confidence depends on how recent, dense and verifiable the local data are.
Where data are thin, old or unverified the reference range can be wide; missing data on the map does not mean there is no plan or no transaction.
Validation figures
- Latest validation: 27 October 2026. Reference prices by commune and ward were updated the same day.
- Samples: 271 valid land listings in Lâm Đồng (212 residential, 59 perennial cropland). The reference price used for checking is the asking price × 0.88, not a notarised sale price.
- Error: 5-fold cross-validation, median absolute percentage error (MdAPE) 42.1%, meaning half of the estimates are within 42.1% of the reference price.
- Ranges: the 80% range shown on the map contains the reference price for 80.8% of samples.
- Error by area (MdAPE): Lâm Hà 30.5%, Đà Lạt 38.8%, Đức Trọng 41.9%, Di Linh 42.7%, Phan Thiết 48.2%, Gia Nghĩa 68.6%, Đạ Huoai 83.2%. Areas with few samples have larger errors.
- There is no independent set of actual sale prices to validate against yet; these figures will be updated when there is.