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# tilingBoundary files

Tiling boundary files are parameter files containing structures of the form:

typedef struct {
int chunk;
int primTargetMask;
int secTargetMask;
int stripe;
char NSBX;
int coordType;
double lambdamu[2];
double etanu[2];
char targetVersion[30];
double firstArea;
} TIBOUNDARYFULL;


Each element represents a rectangle on the sky (or something close to a rectangle); depending on which file it is in, it can represent a region to include (a boundary) or to exclude (a mask). The boundaries can overlap; an object is always said to belong in the *first* boundary which contains it. The specification of the rectangle goes as follows:

• chunk: The spectroscopic survey has been broken up into "Chunks" on which the target/tile pipelines have been run. This parameter indicates which chunk the rectangle belongs to. Masks in a specific Chunk apply *only* to boundaries in that chunk; masks with the chunk specification "-1" apply to all chunks.
• primTargetMask/secTargetMask: The targets flags to which the boundary or mask applies (ie. include such and so objects in this region, or only exclude such and so objects).
• stripe: The survey stripe which the rectangle is near. The survey 10 represents the equator; it is at survey "latitude" eta=-32.5. The centers of the stripes are at eta=stripe*2.5-57.5
• NSBX: If 'B', the area is actually the intersection of the rectangle with the official survey stripe limits (note the dependence on differing North and South stripe limits). If 'X' the full rectangle is used.
• coordType: The coordinates in which the region is a rectangle.
• '0' indicates ra/dec.
• '1' indicates eta/lambda
• '2' indicates nu/mu Great Circle coordinates (inclination set according to "stripe")
• '3' indicates eta/mu coordinates (ie. it is *not* a rectangle in any coordinates; it is defined by the intersection of the constant-eta great circles and the constant-mu great circles)
• lambdamu: The bounding ra/lambda/mu values in degrees (depending on coordType)
• etanu: The bounding dec/eta/nu values in degrees (depending on coordType)
• targetVersion: The version of target used in this region (appropriate for boundaries but not masks). The parameter files for all target versions are stored in the ../target directory.
• firstArea: The area associated with this region in square degrees; this is the area covered by the boundary which was not assigned to boundaries earlier in the list.

The imaging survey geometry can then be expressed as:

\sum_{chunk} ( Boundary_{chunk} - Mask_{chunk} - Mask_{-1} )

where the sum over the chunks indicates a union, and the minus signs indicate that you extract from the boundary the *intersection* of the boundary and the mask.
Last modified: Mon Mar 3 15:22:59 CST 2003