Introduction to Datum
Datum is the singular form of Data. This word is rarely used in day to day routine, and hence it is uncommon among us. Datum can be referred to as a piece of information or the starting point of any work. This can be any reference point from where calculations and measurements can be taken with coordinates’ help. It is important for doing analysis and also to work on predictive analytics based on factual points. In the field of GIS, the Vector and Raster form of information can be defined as a perfect datum. In simple terms, the random parameters that are obtained after performing an experiment or an observation are known as a Datum.
Why do we Need Datum in GIS?
Datum is the most important factor of all in the world of GIS. With the help of field surveying and geodesy, Datum is collected for further analysis. Geodesy is the form of study in the field of Earth science where the experts work on various geological parameters like polar movements, crustal motions and tide movements, etc.
Primarily there are two types; they are as follows:
The horizontal datum for the longitudinal and latitudinal details and Vertical datum to understand the height and the depth of the geographic feature. A geographic Information system is all about geological knowledge, and hence the information collected using all the datum is needed to complete the overall puzzle.
For example, Horizontal data is used to measure the positions on the earth and Vertical data is used to measure the depth of the sea level or elevation mountain.
How to Use Datum in GIS?
Before using and innovating Satellite mapping technology, the best way to calculate the measurements and make projections were based on geoids (Shape of the earth by considering the ocean levels). As the surveying technologies improved and data acquisition methods evolved, the formulae for calculating the features and the geoids also improved.
Earth is not a perfect Sphere. This is causing the problem to define the exact shape of our planet. With the help of calculations, humans have created a datum for simplifying the projection. However, due to many irregularities, different provinces, regions, and countries have their own data set. It helps the geodesists learn about coordinate systems because the datum reference point is saved in coordinate systems. It is saved in the format of DMS, i.e. Degrees, Minutes and Seconds. When the datum is changed, the coordinate values of the Geographic Coordinate system also changes. There are multiple legit and standardized datum that is built by different countries (WGS84, NAD27, BESSEL 1841) With the help of coordinating values, longitudinal and latitudinal information. It can be the same integrated with various geographic Information Systems to understand the different regions’ topography. ArcGIS is the perfect example of a complete Geographic Information System that uses a lot of datum data. The amalgamation of the geographic coordinate system and Global positioning system gets more accurate in identifying the flaws and shifts on the layers.
How Does Datum work in Geographic Information System?
In the Geographic Information System, the data that does not share the same geographic coordinating system in a single map or scene, geographic transformation is needed. Geographic transformation transfers the coordinate values from one geographic coordinate system to another. While working on the data, GIS analysts and technicians add multiple layers to the maps that transform the coordinate values.
When it comes to working in the Geographic Information System, then it refers to only two coordinating systems with respect to transformation. One is the World Geodetic System, and the Other is the China Geodetic Coordinating system. Unlike World Geodetic Coordinating System, There are no customizations available to China geodetic Coordinating system. Enterprise Software Systems like ArcGIS leverages GIS enthusiasts to work on the geographic datum transformation. GIS Analysts and technicians work on all the available coordinate levels and Standard datum calculation while.
GIS Datum helps analysts know the depth of the sea level and measure the height of the mountains. The geographical information related to the height of mountains, length of the river, depth of the ocean and even area of any lake can be saved in the Geographic Information System that is extracted through the datum. Most of the organization build their geographic Information System looking at the base of coordinate values. The information pertaining to the different coordinates is maintained in the Relational Databases of the systems. This information is further used to geocode the maps and solve the loopholes in the existing data.
Advantages of Datum
Below are some advantages of Datum in GIS:
- Geodesists and Surveyors are used to create the reference points for floodplain maps, property boundaries, construction surveys and levee designs (Embankments made for Natural calamities).
- Datum are used in projections like changing of 3D models to 2D models, monitoring of Earth’s crust and also for survey boundary delineation (Survey related boundary of any feature)
- The Global Positioning System uses datum to understand the shifting in the coordinates.
- Geodesists majorly use it to calculate water body movements like tidal movements, Sea level change, and even river width changes.
- Datum helps in making the recurring dimensional measurements.
- It also helps in communicating the part of functional movements and relationships.
Conclusion
This part of the topic is crucial and yet complex simultaneously; hence engineering experts with GIS and mathematics knowledge work on this. There are various calculations and hypotheses derived from the observations and the experiments that are performed. Earth doesn’t have its true shape in a simple sense, so datum helps us know about the spheroid, sphere or elliptical form of earth. There are abstract vertical and horizontal lines on the globe that divide and distribute the region based on the coordinate system. The live and perfect example of a Datum working in the Geographic Information system would be Google Earth.
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