A method of determining a new Position for a Node n, said Node having a distance measuring radio, said method comprising the steps of: a) Starting with a previously determined previous Position P, said previous Position having a previously determined Confidence C, calculating a predicted Position pP, and an associated predicted Confidence pC, said calculations utilizing data from at least a 3-axis inertial sensor, b) Electronically measuring at least a first distance Dn1 to at least a first other Node n1, and at least a second distance Dn2 to at least a second other Node n2, c) Obtaining the current Position Pn1 of at least said first other Node and Position Pn2 of at least said second other Node, said Position comprising at least X, Y, Z coordinates and a Confidence metric Cn1 and Cn2, d) Geometrically projecting the distances Dn1 and Dn2 onto a common horizontal plane, to determine projected distances pDn1 and pDn2, characterized in that the method further comprises the steps of: e) Calculating Circle-Circle Intersections of said projected distances to determine two candidate Positions cPa and cPb, f) Determining a candidate Confidence cC as the lesser of Cn1 and Cn2, then adjusting said Confidence cC based on geometric conditions of the calculations in step e), g) Determining the error distance eDa between pP and cPa, and error distance eDb between pP and cPb, h) Choosing the candidate Position with the lesser error distance as the candidate Position cP, i) If confidence cC is greater than pC, choosing candidate position cP as new position P and taking cC as the new confidence C, otherwise choosing predicted position pP as new position P and predicted confidence pC as new confidence C. a) Starting with a previously determined previous Position P, said previous Position having a previously determined Confidence C, calculating a predicted Position pP, and an associated predicted Confidence pC, said calculations utilizing data from at least a 3-axis inertial sensor, b) Electronically measuring at least a first distance Dn1 to at least a first other Node n1, and at least a second distance Dn2 to at least a second other Node n2, c) Obtaining the current Position Pn1 of at least said first other Node and Position Pn2 of at least said second other Node, said Position comprising at least X, Y, Z coordinates and a Confidence metric Cn1 and Cn2, d) Geometrically projecting the distances Dn1 and Dn2 onto a common horizontal plane, to determine projected distances pDn1 and pDn2, e) Calculating Circle-Circle Intersections of said projected distances to determine two candidate Positions cPa and cPb, f) Determining a candidate Confidence cC as the lesser of Cn1 and Cn2, then adjusting said Confidence cC based on geometric conditions of the calculations in step e), g) Determining the error distance eDa between pP and cPa, and error distance eDb between pP and cPb, h) Choosing the candidate Position with the lesser error distance as the candidate Position cP, i) If confidence cC is greater than pC, choosing candidate position cP as new position P and taking cC as the new confidence C, otherwise choosing predicted position pP as new position P and predicted confidence pC as new confidence C.