Articles in the Geodesy Category

Dec 2005 | Comments Off on Signal propagation through the ionosphere

The Indian ionosphere is characterized by large horizontal gradients, intense irregularities, large dayto- day variations and equatorial anomaly conditions, there is clear necessity to thoroughly understand the ionospheric time delay effects on the GPS signals. The ionospheric delay error is a function of Total electron content (TEC) which is one of the dominant errors.

Dec 2005 | Comments Off on Geodetic commentary

The Mix up of “X, Y, Z” Coordinates Between Photogrammetry and Geodesy
In Spatial considerations –
In geodesy, the “ZXY” coordinate system is “right-handed”, where the right thumb points towards the Z-axis, index finger towards the intersection of the Reference Meridian and Equatorial planes, and middle ?nger or the positive Y-axes, which is …

Dec 2005 | Comments Off on Geodetic Misunderstanding

1. Spheroid is considered equivalent to an ellipsoid.
2. The longitude at the North or South Pole is zero degree.
3. The Mean Sea Level (MSL), a time-variant “average”, is
considered as time-invariant and time-independent.
4. The measured “dn” along a spirit level loop sum up to zero.
5. Imagine a freely ?owing ocean or sea channel under
a continent and it represents the Geoid.
6. The geoidal undulation or height (N) is equivalent to orthometric height (H).
7. There are “yours” and “mine” geoids. In other words every country has its
own geoid, creating a “political” boundary value problem for gravity.
8. When one has to re-observe at any station, it does not make any
difference so long one is observing within “few” meters.
9. If one asks for and gets a height as “123.4 m”. It is OK to add
zeros at the end, e.g., 123.4000, to make it more accurate.

Nov 2005 | Comments Off on Signal propagation through the troposphere


Space environmental effects on satellite communication can be considered as related to space segment, ground segment and on the signals propagating through the earth’s lower and upper atmosphere. The atmospheric structure has significant influence on signal propagation. This has definite influence on the data processing methodologies. The specific applications with which are concerned here are …

Oct 2005 | Comments Off on CLASSROOM GEODESY

The Coordinates Class room espouse readers to graticules of Mathematics and Physics that epitomize the Geospatial Information Technology. A chain of structured presentations related to interdisciplinary principles that define Geodesy, GPS, GIS, Geospatial data management and Image processing are to be en suite in this section in each issue of the Coordinates. Initially the chain …

Oct 2005 | Comments Off on International Terrestrial Reference Frame (ITRF)

The International Terrestrial Reference Frame (ITRF) “yy” is a realization of the International Terrestrial Reference System (ITRS), where the “yy” represents the year of the solutions. Since its fi rst realization in 1988, there have been many variations and additions in use of data types and changes in computational strategy.
International Earth …

Sep 2005 | Comments Off on The old Indian Datum

Under the new Map Policy, it seems that India has decided to retain the old Indian Datum, which has been identified by “Everest”, for DSMs. The following geodetic definition issues and “specifi cations” are worth commenting:
Vintage – 1880s.
Name – On a recent enquiry, four SOI experts provided four different names. However, it cannot be “Everest”.
Spheroid …

Sep 2005 | Comments Off on Malaysia precise geoid (MyGEOID)

GPS infrastructures that have been established in Malaysia are mainly served as a ground control stations for cadastral and mapping purposes. Another element that has not been utilised is the height component due to its low accuracy. Conventional levelling is still the preferred method by the land surveyors to determine the stations orthometric height (H) with a proven accuracy. Therefore, Department of Survey and Mapping Malaysia (DSMM) has embarked the Airborne Gravity Survey, with one of the objectives is to compute the local precise geoid for Malaysia within centimeter level of accuracy. With the availability of the precise geoid, the “missing” element of GPS system is solved.

Aug 2005 | Comments Off on Classroom Geodesy

In continuation of the discussion about the ellipsoid and geoid in the earlier interaction through the Classroom feature, let us define the reference coordinate systems. Consider a vertical axis oriented towards the north pole as Z axis. The X axis is oriented towards the First point of Aries ?. The Y axis completes a right …

Aug 2005 | Comments Off on Mumbai Floods: Another wake-up call

Maharashtra was the first state in the country to have a disaster management plan. It all started with the Latur Earthquake of 1993. As a part of response programme, the Maharashtra Emergency Earthquake Rehabilitation Project (MEERP) was launched the same year. This later led to the exercise of preparing a State Disaster Management Plan. The World Bank, United Nations Development Program (UNDP) as well as several bilateral donor agencies supported the initiative.