Here is a situation that happens more often than it should:
A client receives a GIS shapefile from one consultant. They bring in another consultant who collects new survey data. When both datasets are loaded into the same GIS, the features are 50 metres apart — even though they are supposed to represent the same things.
Nobody did anything obviously wrong. Both datasets have coordinates. Both were collected with proper equipment. But they are in different coordinate systems, and nobody noticed until the data was combined.
This kind of problem costs time, money, and sometimes causes decisions to be made from incorrect data. It is entirely avoidable once you understand what is happening.
The earth is not a flat surface and it is not a perfect sphere. It is an irregular oblate spheroid — slightly flattened at the poles, with mountains, valleys, and a gravitational field that varies from place to place.
To assign coordinates to points on this surface, we need to:
Different countries, different time periods, and different applications have made different choices about all three of these. The result is dozens of coordinate systems in common use — and data that looks correct but does not align when combined.
The first distinction to understand is between geographic and projected coordinates.
Geographic coordinates (latitude and longitude) describe position on the curved surface of the earth. Latitude runs from -90° (South Pole) to +90° (North Pole). Longitude runs from -180° to +180° from the Prime Meridian at Greenwich.
Geographic coordinates are universal and intuitive, but they have a problem: degrees are not a fixed unit of distance. One degree of latitude is about 111km anywhere on earth. But one degree of longitude at the equator is 111km, at 30° latitude it is 96km, and at 60° latitude it is only 56km. You cannot measure distances or areas directly from geographic coordinates without trigonometry.
Projected coordinates are geographic coordinates mathematically transformed onto a flat plane. The result is coordinates in metres (or feet) that you can use directly for distance and area calculations.
Every projection distorts something — shape, area, distance, or direction — because you cannot flatten a sphere without distortion. Different projections are optimised for different purposes and different parts of the world.
World Geodetic System 1984. This is the global standard — the datum used by GPS satellites. When your phone or GPS receiver gives you coordinates, they are in WGS84.
WGS84 is what you should use for most modern GIS work. It is globally consistent and compatible with satellite data sources.
This is the legacy datum used for historical survey work in East Africa, including most Survey of Kenya mapping from the mid-20th century. If you are working with old cadastral maps, government title deed coordinates, or data from surveys done before the widespread adoption of GPS, the coordinates are likely in Arc 1960.
The shift between Arc 1960 and WGS84 in Kenya is approximately 120–170 metres depending on location. This is the source of many data alignment problems. When someone loads old cadastral data next to GPS-collected data without performing a datum transformation, the features are in the wrong place by roughly this amount.
Every coordinate system has an EPSG code — a number assigned by the European Petroleum Survey Group that uniquely identifies it. When working with GIS data, always record and communicate the EPSG code.
Common codes you will encounter in Kenya:
| Coordinate System | EPSG Code |
|---|---|
| WGS84 Geographic | 4326 |
| WGS84 / UTM Zone 37S | 32737 |
| WGS84 / UTM Zone 36S | 32736 |
| Arc 1960 / UTM Zone 37S | 21037 |
| Arc 1960 Geographic | 4210 |
Most of Kenya falls in UTM Zone 37S. The western parts of the country (west of 36°E longitude) fall in Zone 36S.
For most survey and GIS work in Kenya, the appropriate projection is WGS84 / UTM Zone 37S (EPSG:32737).
This gives you:
For projects in western Kenya, use Zone 36S. For continental or regional-scale analysis, consider using an equal-area projection like Africa Albers Equal Area Conic.
In QGIS:
If your data has no CRS defined, you will need to investigate. Check:
Most GIS software can transform data between coordinate systems. In QGIS, use Vector → Data Management Tools → Reproject Layer.
Important: Always transform to a standard system rather than mixing systems in the same project. Define your project CRS at the start and ensure all data is transformed to it before use.
When transforming from Arc 1960 to WGS84, use a proper grid shift file if available. QGIS uses the PROJ library for transformations, and the quality of the transformation depends on the transformation parameters used. For critical work, verify that transformed coordinates match field-surveyed WGS84 coordinates.
Before starting any GIS or survey project:
This takes five minutes at the start of a project. Not doing it can cost days of rework.
If you are working with legal documents — title deeds, survey plans, subdivision applications — coordinate system questions have legal implications. Survey plans filed with the Survey of Kenya must use the prescribed coordinate systems and datum transformations. Getting this wrong does not just produce misaligned maps. It can invalidate a survey or create boundary disputes.
For any work involving official land documents, work with a licensed surveyor who understands both the technical and regulatory requirements.
ZeroPoint Geospatial delivers all survey data in clearly documented coordinate systems, with datum transformation performed where required. We provide data in your preferred format and CRS. Contact us for survey and GIS services.