Due to increasing population and land prices, people occupy state owned lands in many countries. Therefore, the question is how efficiently can RS and GIS technologies can be benefited for quick identification of such illegal occupants?
first you need to know which is the state land. I am not sure if satellites are intelligent enough to identify (on a lighter note).
If the intention is to see encroachment it will better be done using a satellite derived product like a landcover map and change detection can help identify settlements in areas which are government owned. I think lots of manual input is required in thsi cannot be solely automated.
I honestly dont think that is any "efficient", "quick" or "automatic" way to identify those typologies of settlements.
Mentioned ArcGis functions are very generally and will easily fail in that tasks.
Ancillary data such as land property layer might help, but they could also be unsufficient as public lands can be purchased by private developers, so you cannot be sure id that development is illegal or is a direct consequence of a legal acquisition by those private developers.
I agree with the previous comments that RS alone is difficult without auxiliary information such as a cadastral layer. The main problem is that such datasets because of its sensitive nature is seldom released for public consumption. As much as I like RS technology it does have its limitations.
I do not think the time series data would have any help since it can only detect the change in settlement or habitat sizes. How this can be attributed to legality. You can only detect the illegal occupant if you have cadestre of legal settlements updated with housing units and blocks. Any new construction on the ground can be tracked by using RS data. But this can also be error prone. You might also stake help of street cameras and field data to identify the occupants. There is thin possibility using multiple technology. Unless we ensure proper and secure entry to the state we cannot track the visitors. Settlement needs to be mapped and faster high resolution data can be used to detect the change which might only give you starting data for further investigation.
I dont think as said earlier legality of setellment can be chacked from satellite image alone. Take a landuse (urban planning map and integrated it with recent satellite data, if anything falls outside in areas which are not suppose to be constructed, that si encroachment.
What is important is the reference first. If there is a base map already available and legality is established then on ground possessions can be checked and verified whether legal or illegal occupancy. In Pakistan, state own land mostly held by tenants for years (even 100 years) lease. Because of analog record keeping system and slow judicial process, its difficult to track the legal or illegal occupancy. RS/GIS may help when there is digital record available.
Land encroachment can be checked and control by making sure that all land users encouraged to properly and legally survey and register their properties by employing the professional services of qualified, experienced and registered / licensed Land Surveyors.
Possible problem could be that some properties are either not surveyed and registered and surveyed at all or are done illegally by quacks or unexperienced, not registered surveyor. It could also be that some properties were completed before digitisation of state maps were implemented, resulting to a possible non-inclusion of existing analogue maps in the state GIS Database.
Unless otherwise, then both existing maps and new surveyed properties should be checked and controlled against a standard state GIS maps. Therefore anything falling outside this should be marked and recorded for further possible legal process. If these were earlier surveyed, then the name of the survey company be requested to enable a proper legal process.
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