The Carrizozo and McCartys basaltic lava flows in central New Mexico are excellent sites to study the emplacement of long compound flow fields. Differential Global Positioning System (DGPS) data of both flows have revealed new details about the relief and emplacement of these compound basaltic flows. The topographic data, with horizontal and vertical precision of [about] 2 to 4 cm, show distinctive terracing along the flow margins in the proximal and distal portions of both flows, interpreted to be indicative of multiple episodes or scales for the local flow emplacement a topographic transect across the Carrizozo flow along Highway 380, [about] 10 km down flow from the vent, supports the interpretation that multiple flow elements banked against earlier episodes to build the field from east to west. Topographic measurements of the McCartys flow are consistent with results obtained for the Carrizozo flow, and help to constrain how the eruptions may have produced both flows. The dimensions of a very narrow neck on the McCartys flow, [about]40 km down flow from the vent, provide strong constraints on the lava tubes that must have fed the distal portions of the flow, resulting in a maximum likely effusion rate of [about]500m3/s. At Carrizozo, a single medial ridge along the narrow central portion of the flow can be interpreted as a collapsed lava tube similar to the McCartys flow neck, which suggests a maximum likely effusion rate of [about]800m3/s. Both flows could have been emplaced at these rates within a period of a few months. The observations and inferences at Carrizozo and McCartys have implications for long lava flows observed om other planetary surfaces.