You are correct in that imaging a round earth on a flat screen must
involve projection. However, there is no one projection that is fit for
all purposes so it is pretty normal to store data sets in GCS and
project on-the-fly into whatever projection is fit for purpose. To
complicate matters, describing the position of a point on the planet in
lat/long means also defining a figure for the ellipsoid which is still
an approximation for the real object, and furthermore our planet is
dynamic so points move over time. This means there is no one, true GCS
though for most purposes the WGS84 framework with a suitable time
reference is new measurements. However historical data is likely to be
measured on a local datum with earlier best-guess figure of earth but I
digress.
There is nothing to stop you however from treating lat/long as
rectangular coordinates and using that as a "projection". The projection
figure is Plate Carree and this has no redeeming cartographic features
as a projection. It is however, obviously exceedingly easy to calculate
so could be regarded as "programmer" or "computer resource" friendly.
For a quick look at some data it okay, providing you understand what you
are looking at.
Hi all, I am a novice to geospatialrelated terminology...and going
through some literature to understand better.. Could someone please tell
difference btwn geographic and projected coordinate system... I mean, I
am not able to imagine how I can see an (satellite) image on screen (
flat surface) and say it is in geographic cordinate system (GCS)... as
GCS means lat/long and I see it on a flat screen, so should it not be
projected if I am seeing it on a flat screen? And if it is projected,
then how can it be in GCS ? My doubt, perhaps , may sound very trivial
for all the experts out there but I will really appreciate anything that
will aid my understanding. Thanks. -- View this message in context:
http://osgeo-org.1560.x6.nabble.com/geographic-vs-projected-coordinate-system-tp5059024.html
Sent from the GDAL - Dev mailing list archive at Nabble.com.
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