Distinguish size from precision and radius
04SIZE describes a sphere enclosing the entity. Horizontal and vertical precision describe uncertainty in the reported center; neither is an authentication guarantee.
Separate 0xA1 has a nibble greater than 9 and 0x01 has zero base with nonzero exponent. The fixture refuses to assign distances to these undefined values;0x00 means less than 1 cm, not a proven zero-size object.
Source for this drawing: RFC 1876 · Read RFC section 2 ↗
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A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
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Terms in this drawing
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
Each size/precision byte has a high-nibble base and low-nibble exponent: base×10^exponent centimeters. Nibbles greater than 9 and zero-base/nonzero-exponent combinations are undefined.
- Each size/precision byte has a high-nibble base and low-nibble exponent: base×10^exponent centimeters. Nibbles greater than 9 and zero-base/nonzero-exponent combinations are undefined.
- SIZE is a diameter. Horizontal precision is the diameter of a circle of error, and vertical precision is total potential vertical error. A plus-or-minus magnitude is half the stored amount.
- 0x00 represents less than 1 cm;0x15 means 1×10^5 cm=1000 m. The format uses coarse decimal increments; the sample AppendixAconversion is not a general validating parser.
Examples are fictional, offline teaching fixtures. RFC1876 is Experimental; its classful IPv4 fallback is historical, not universal current geolocation. Follow the linked official sections for full requirements.
Read the RFC section ↗