If you create a spatial reference system
and any of the coordinates that you are working with are decimal values,
calculate the appropriate scale factors for your coordinates and measures.
Scale factors are numbers that, when multiplied by decimal coordinates
and measures, yields integers with at least the same number of significant
digits as the original coordinates and measures.

## About this task

After you calculate scale factors, you need to determine
the extent values. Then submit the db2se create_srs command
or call the DB2SE.ST_CREATE_SRS procedure.

## Procedure

To calculate the scale factors:

- Determine which X and Y coordinates are, or are likely
to be, decimal numbers.
For example, suppose that of
the various X and Y coordinates that you will be dealing with, you
determine that three of them are decimal numbers: 1.23, 5.1235, and
6.789.

- Find the decimal coordinate that has the longest decimal
precision. Then determine by what power of 10 this coordinate can
be multiplied to yield an integer of equal precision.
For
example, of the three decimal coordinates in the current example,
5.1235 has the longest decimal precision. Multiplying it by 10 to
the fourth power (10000) yields the integer 51235.

- Determine whether the integer produced by the multiplication
just described is less than 2
^{53}. 51235 is not
too large. But suppose that, in addition to 1.23, 5.11235, and 6.789,
your range of X and Y coordinates includes a fourth decimal value,
10000000006.789876. Because this coordinate's decimal precision is
longer than that of the other three, you would multiply

this coordinate-not 5.1235-by a power
of 10. To convert it to an integer, you could multiply it by 10 to
the sixth power (1000000). But the resulting value, 10000000006789876,
is greater than 2

^{53}. If

Db2® Spatial Extender tried to store it, the results would be unpredictable.

To
avoid this problem, select a power of 10 that, when multiplied by
the original coordinate, yields a decimal number that Db2 Spatial Extender can truncate to a storable
integer, with minimum loss of precision. In this case, you could select
10 to the fifth power (100000). Multiplying 100000 by 10000000006.789876
yields 1000000000678987.6. Db2 Spatial Extender would round this number to 1000000000678988, reducing its
accuracy slightly.