Location-specific attributes e.g. infrastructure play an important role in real estate application like property value analysis and site selection. Geographic Information System (GIS), a platform that links the computerized mapping, spatial data and database management system, is thus extremely useful for real estate applications.
Why Spatial Data Quality
However, the most fundamental steps which is both time consuming and costly (to certain extent), for real estate practitioners that keen to initiate a GIS is creating a database. In order to provide reliable and relevant output, the precise and accurate integration of spatial data is crucial to real estate practitioners.
As such, understanding and checking the spatial data quality (SDQ) is important for real estate projects uses GIS even prior to acquiring the data and after data development.
The consequences of poor handling in Spatial Data Quality
The common mistakes that one can make in implementing a GIS are data collection and compilation errors, data processing errors and data usage errors. The presence of errors would result in wrong analysis and misappropriate conclusions, are sometimes unavoidable. But it could be mitigated suitably if users are aware of the limitations by execute proper quality criteria e.g. accuracy versus completeness and leverage on available supports e.g. SG-SPACE to estimate the quality of data provided by a source with another source.
Components of Spatial Data Quality (SDQ)
Next, for clarity, the author would attempt to illustrate SDQ in the real estate context. Generally, the components of SDQ include: (1) Lineage, (2) Positional accuracy, (3) Attribute accuracy, (4) Logical consistency & (5) Completeness.
Lineage
For (1), this is referred to the source and process used to derive the data e.g. surveying or cartography. In the example of surveying, considering the methods of derivation, the land surveyor might not be able to access to the area due to uncontrollable situations e.g. military area or the data might not be updated e.g. fails to capture new buildings. It could result in wrong assumptions made by real estate users in determining the highest and best use.
Positional accuracy & Attribute accuracy
For (2), this is the closeness of a feature to its true position in an appropriate coordinate system. It could be expressed as 95% of the land parcel corner points in a parcel layer are ± 3m of their true location. In this case, it is dependable of (1), as the scale and resolution of the source are the determinants of (2). In other words, if the source e.g. maps are less precise or lack of standardized scale, the GIS layer is almost always less accurate to pinpoint the actual location. From economic perspectives, it could result in huge bid price difference, said, between the distances to CBD e.g. 2km versus 20km in map dimension.
While for (3), an attribute provide information includes the fact about the set of locations e.g. population or measurement e.g. elevation that are necessary for market/site studies. Typical errors occur include typo error, numerical error e.g. wrong values, categorical error e.g. replace land use type from “residential” to “industrial”. For the latter, the operator may be held negligent for developer’s loss.
Logical Consistency & Completeness
Next, (4) deals with the attribute rules for spatial data and logical rules of structure/framework, it also describes the compatibility of a datum with other data in a data set. There might be issues if there is inconsistency exists. For illustrations, if there is gaps or overlaps between census area, the population forecast will be invalid.
To ensure the data quality, logical consistency checks such as metric incidence and incidence tests could be run. Lastly, (5) is a check to ascertain if there is any omission of relevant data. Taking retail study as an example, it is to check whether all shopping centers are captured in the database, including mixed development.
Work with Spatial Data Quality’s potentials and limitations
By understanding SDQ, users could sometimes prevent errors. Some methods include use default values (to prevent typo errors), required fields (to prevent omission) & manual check against sources. Importantly, operators should document the data quality in metadata that provide information such as the sources, last update, the purpose for the data.
Such actions would often reveal the usefulness and flaws of the data, so as to allow future users to make informed decisions.
Summary
In summary, for real estate users to successfully exploit and harness the GIS capability, would requires operators to balance between artificial intelligence e.g. auto computation and human judgment on GIS, an enabled platform.
Reference:
Spatial Information ClearingHouse (2004). Spatial Data Topics. Retrieved February 13, 2011, from http://maic.jmu.edu/sic/topics.htm
Author: Lawrence Ler