Server Side Processing Functions

geogrid

The geogrid() function applies a constraint given in latitude and longitude to a DAP Grid variable. The arguments to the function are:

geogrid(variable, top, left, bottom, right[, expression ...])

The variable is the data to be sub-sampled. The Top, left, bottom, right are the latitude and longitude coordinates of the northwesterm and southeastern corners of the selection box. The expressions consist of one or more quoted relational expressions. See grid() for more information about the expressions.

The function will always return a single Grid variable whose values completely cover the given region, although there may be cases when some additional data are also returned. If the longitude values 'wrap around' the right edge of the data, then the function will make two requests and return those joined together as a single Grid. If the data are stored with the southern latitudes at the top of the array, the return result will be flipped so that the northern latitudes are at the top.

grid

The grid() function takes a DAP Grid variable and zero or more relational expressions. Each relational expression is applied to the grid using the server's constraint evaluator and the resulting grid is returned. The expressions may use constants and the grid's map vectors but may not use any other variables. In particular, you cannot use the grid values themselves

Two forms of expression are provided:

1. "var relop const"
2. "const relop var relop const"

Where relop stands for one of the relational operators, like = and >

For example: grid(sst,"20>TIME>=10") and grid(sst,"20>TIME","TIME>=10") are both legal and, in this case, also equivalent.