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Satellite Projections


This page is about satellite projections. It has nothing to do with satellite data. Not all satellite data can be plotting using NCL. Examples of available techniques include:
sat_1.ncl: Creates a dramatic plot of sea level pressure over a satellite view of the earth with H and L labels.

cnHighLabelsOn = True
cnHighLabelFontHeightF = 0.024
cnHighLabelBackgroundColor = -1
Turns on High labels, controls their font size and background color. For Low labels, just swap out High for Low.

cnLabelDrawOrder, Draws the contour info labels on top of the contour lines. Since the labels in these plots have white backgrounds, this is very useful.

mpProjection = "satellite", Selects the map projection. There are other projections to choose from.

mpSatelliteDistF=3.0, This resource specifies the distance in multiples of the earth's radius of the satellite at the view origin. If the value is 1.0 or less, the satellite projection is replaced by its limiting case: an orthographic projection. The default is 1.0.

mpOutlineBoundarySets ="National", Adds country boundaries to the continental outlines. There are other types of outlines to choose from.

mpGridLineDashPattern = 2, Changes the lat/lon lines to dash.

sat_2.ncl: This second is very similar to the first example except that some shading has been added to emphasize the high pressure areas.
sat_3.ncl: Example of how to zoom in on a satellite projection plus a demonstration of the new automatic tickmarks.

In order to zoom in on a region the four resources
mpMinLatF, mpMaxLatF, mpMinLonF, and mpMaxLonF must be set. The thing to remember, is that mpLimitMode must also be set to "LatLon". The csm cylindrical equidistant and polar stereographic plot templates set this resource for you, so it is easy to overlook.

pmTickMarkDisplayMode = "Always", will turn on the automatic lat/lon labels. This is primarily useful for projections other than cylindrical equidistant and polar stereographic which have been given their own style of lat/lon labels by the csm plot templates.

mpGridAndLimbOn = True, turns on the lat/lon grid which was turned off by the plot template.

mpGridMaskMode = "MaskLand", will mask the grid over land so that it is only visible over water.

mask_6.ncl: This example shows how to use the "Angles" value for mpLimitMode, along with mpSatelliteAngle1F and mpSatelliteAngle2F to zoom in on a satellite projection.