System Unification for Geodetic Survey and Cadastral Survey

I. OVERVIEW

Talking about cadastral survey, we always remember about survey for land certificate. This method is used for small area measurement. In Indonesia, cadastral survey identically with no reference measurement. Surveyor can measure every land without geodetic consideration (minimum distance, ellipsoid, datum, reference control point, height and so on)

On the other hand, geodetic survey that is conducted by "science" agency always use geodetic consideration. Reference points, height measurement are the two factors that always follow geodetic survey.

I think this condition is ironic, because they measure the same object but for different purpose. So, what are the disadvantages from this conditions ? There are overlapping work that have been done by different agencies. The second disadvantages is the uselessness of geodetic infrastructures.

So many geodetic infrastructures that have been built by the government become useless because cadastral surveyors do not use these infrastructures. Why they do not use these infrastructures ?

One of the factor that they do not use geodetic infrastructures is that they do not know about the principal of land surveying and mapping. They just know how to measure lands, make a scale and than draw the land. They do not think about the point reference in land surveying and mapping in the good coordinate system.

On the other hand, the most important thing in the cadastral surveying is that the result of survey has to be able to be reconstructed. So, the cadastral result has to containt a good surveying method (using geodetic considerations), a good mapping method (using coordinate system) not just using local system.

Has to be able to be reconstructed itself means that the result of cadastral survey has legal aspect as a proof if someday there will be a land conflict. So, whatever the purpose of cadastral survey (for tax or land certificate), geodetic considerations should be used in every cadastral survey.

II. GEODETIC CONSIDERATIONS

A good survey and mapping has to use geodetic pattern. First of all, before surveyors measure the land, they have to make sure that the land that they will be measured are able to "lay down in the one reference system". It means that all land that have measured must be integrated in the one coordinate system.

If the land or area does not have reference points, surveyor has to make reference points first. For good surveying, it must be 2 reference points for minimum constraint. These reference points have function as a reference for surveyor to do survey. Reference here means that these reference points already have coordinate in global system.

Cadastral survey always use assumption that the earth is flat. This assumption is totally wrong. Earth is not flat. In some particular distance (111 km), the around effect of the earth has to be considerated in coordinate computation. So, if the area of measurement is more than 111 km, the coordinate computation has to used geodetic consideration.

In this particular thing (geodetic consideration), geodetic distance, geodetic lines, projection system are the most common computation in determining coordinate. But commonly, cadastral activities do not use these.