UAV ( Drone) Photogrammetry and GIS for Property Tax Base Assessment
Updated: Apr 19, 2020
The local government system in Ghana is premised on the idea that Metropolitan, Municipal and District Assemblies (MMDAs) acting as rating or development authorities are responsible for financing development activities in their jurisdiction. As rating authorities , they raise funds by collecting revenue in the form of taxes, user fees and licenses among others on properties and economic activities. These revenue constitute what is generally known as the Internal Generated Funds (IGFs). Property tax is widely viewed as the most significant and potential source of revenue.
Problems Confronting MMDAs
Although property tax is a significant component of all MMDAs IGFs, most MMDAs are fronted with numerous challenges when it comes to property tax mobilization . One of such challenges is the inability of MMDAs to accurately assess their property tax base. Without adequate information on the number, type and the use of properties, MMDAs cannot accurately calculate their tax base. Therefore, for effective property tax mobilization, MMDAs need to know the number of rate-able properties in their jurisdiction etc. Currently, the methods being used are time consuming and cost ineffective.
High resolution aerial footage of a section of Atimatim
Drone Photogrammetry and Property Tax Evaluation
ZGRS embarked on this project as a Proof Of Concept (POC) to demonstrate to Afigya Kwabre South District Assembly (AKSDA) in the Ashanti Region of Ghana on how UAV photogrammetry combined with Geographic Information System can be used in property tax base assessment. The focus of the assessment was to calculate the property tax base in Atimatim which is one of the 57 communities in the district and compare it with actual tax collected.
Profile of Piloted District
Afigya Kwabre South District Assembly (AKSDA) is one of the local government areas in Ashanti region of Ghana with a total area of about 138 square kilometers. Its central location within the Ashanti region and closeness to Kumasi, the second largest city in Ghana, makes it a dormitory district. As a result of high population growth in the district and its closeness to Kumasi, towns such as Atimatim, Maase, Kodie and Afrancho are gaining an urban status. Therefore, there is a potential for increased properties and rising property values in these areas.
Afigya Kwabre South District in Ashanti Region Context
In Phase 1: Preliminary study was undertaken to gather information on the approach for calculating tax base, the criteria for rating properties and the total amount of property tax collected in the previous year ( 2019).
Phase 2: Drone photogrammetry made it possible to produce orthophoto showing all properties in the piloted area. We used our drone (mounted with GPS) to fly over the area at an elevation of 200 meters. Then we used photogrammetry techniques in the Agisoft software environment to perform interior and exterior orientation, triangulation and orthophoto.
Interior & exterior orientation and triangulation in Agisoft
Orthophoto of Atimatim ( Piloted Area)
Phase 3: The orthophoto image of the piloted area was imported into the ArcGIS software for visualization and digitization. Properties ( Parcels) were digitized as seen in the drone raster image without making any distinction between residential, commercial among others considering the time available. Ideally, for appropriate tax base calculation parcels must categorized based on their uses since each use has it own rate.
Digitization of property parcels in ArcGIS environment
Property Valuation and Tax Collection
Valuation of building or property is the method of calculating the present marketable cost of a building. This depends on several factors such as the type of structure, location, size and the type of use it is put to among many others. In Ghana, properties are mostly rated on the basis of the value of the building ( number of rooms if residential). In Afigya Kwabre South District Assembly ( AKSDA) , the annual fee fixing rate per room for a property that serves residential purpose is GH 30 ( $ 6). Depending on the number of rooms in a particular property the annual tax on the property will be calculated as
Number of rooms per building x fee fixing rate = No. Rooms x GH 30.
For commercial properties, the annual rate per room space in the property is equivalent to GH 50. Thus for a commercial property with 5 room spaces, the tax rate will be calculated as
Commercial Tax Rate = No. of room space x GH 50
= 5 x 50
= GH 250 cedis = $ 47
From the preliminary study ZGRS identified that the total property tax collected in the District for the year 2019 was equivalent to GH 150, 000 cedis = $ 27,777.78. In the absence of geo-data and payment tracking mechanism, it was difficult to identify how much was collected from the piloted are since no data existed on this.
Mapping and Digitization
Total area covered during mapping was approximately 7 sq. km.
Images acquired = 600+
Total flight duration was 2hours
Total time taken to process the image = 6 hours
In all, about 3200 parcels were mapped in the piloted area.
Property Tax Base Estimation in the Piloted Area
We assumed that if there is an annual flat fee of GH 30 cedis to be paid irrespective of the the type of property in question within Atimatim, potential property tax base in Atimatim will be calculated as
Total No. of Parcels x the annual flat fee = 3200 x GH 30 cedis
= GH 96,000 cedis
Should the type of properties in Atimatim be taken into consideration in this calculation, then the current potential property tax base of Atimatim will be equivalent to or far exceed GH150,000 cedis which is the total amount of property tax collected in the entire district in the year 2019.
Impact of our Drone Photogrammetry and Geographic Information System for Property Tax Base Assessment
Quick: The first key metric to understand the impact of our approach is that it is quick and efficient compared to traditional or conventional property mapping and digitization.
Digitalized data: Additionally, digitalizing data is also synonymous to preserving it for future scope and opening up new frontiers of application.
Accurate and Exhaustive data: Traditional surveying or mapping only measure individual points. One drone flight produces thousands of measurements, which can be represented in different formats (orthomosaic, point cloud, DTM, DSM, contour lines, etc). Each pixel of the produced map or point of the 3D model contains 3D geo-data
Map otherwise inaccessible areas: An aerial mapping drone can take off and fly almost anywhere. You are no longer limited by unreachable areas, unsafe steep slopes or harsh terrain unsuitable for traditional measuring tools. You do not need to close down highways or train tracks. In fact, you can capture data during operation without an organizational overhead.
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