Frequently asked question

# Why are LAYER tag values rounded in the ArcXML Programmer's Reference Guide?

Last Published: April 25, 2020

## Answer

The ArcXML Programmer's Reference Guide rounds some values in the NOTES section of the LAYER tag. This guide can be located at one of two places:

1. Page 341-342 of \ArcIMS3.1\Documentation\ArcXMLGuide3.1.pdf.

or

2. Through an Internet browser by clicking on Start > Programs > ESRI > ArcIMS 3.1 > Documentation > ArcXML Guide.
The following is a list of actual values used internally by ArcIMS:

A) Meters in an inch = 1/39.37 to the extent of a double-precision float, or
0.0254000508001016.

B) Calculating pixel size = Double-precision floats.

C) Relative scale values:

All internal calculations are done in double precision, and the number is rounded off to the nearest integer (or Long).

D) Feet in a meter = 12 * (1/39.37) in double precision, or 0.304800609601219.

E) Earth's circumference = 40,030.174 meters.

F) Meters to degrees = Multiply meters by 0.000008993220293.

G) Degrees to meters =

'an "l" or a "d" on variables for Long
'and Double, respectively.
'dPI is 3.14159265358979, as a double
lNumHalfCircles = (dDegrees / 180)
dRemainder = dDegrees - (lNumHalfCircles * 180)
L = ((dRemainder* dPI) / 180) / 2 'Deg2Rad / 2
dSL = sin(L)
dCL = cos(L)
dDistanceInMeters = (20015077.0 * lNumHalfCircles) + _
(12741994.0 * atan(sqrt((dSL*dSL)/(dCL*dCL))))

Article ID:000004320

Software:
• Legacy Products

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