### Display antenna position

Observing modes typically involve the antenna to track a given position (per subscan) or drift on sky (also per subscan), and switching between these track/on-the-fly subscans. Given the fact that the sky rotates in all cases, this results in typical patterns when looking at the antenna position. It can be displayed with

    MRTCAL> @ plot-drifting-positions iram30m-wilma-20100930s201-imb.fits

The result is shown in the Figure 7. Under normal conditions, tracked subscans should track a single position during the subscan. On the other hand, on-the-fly subscans continuously drift on the sky. Depending on the observing mode, we can see ON (tracked or OTF) alterning with OFF (tracked) subscans.

Figure 7: Resulting plot of the procedure @ plot-drifting-positions. X axis is time, Y axes are longitude, latitude, or commanded elevation. It displays i) the LONGOFF (relative longitude) of the antenna during the scan - the plot is divided in 2 parts as it is a common behavior to alternate between 2 longitudes from one subscan to another - , ii) the LATOFF (relative latitude) of the antenna during the scan, iii) the CELEVATIO (commanded elevation) during the scan, iv) the “on-source” time coverage of each subscan (as vertical red lines). This example is a typical tracked scan with 12 subscans alterning between ON and OFF positions (LONGOFF and LATOFF are constant in each subscan, but CELEVATIO drifts as Earth rotates.).

Figure 8: Same as Fig. 7, but for a typical On-The-Fly scan with 35 subscans alterning short OFF position, long scanning in a direction, long scanning in the opposite direction, short OFF position, and so on (ROOR repeated sequence). Short OFF subscans have relative coordinates.

Figure 9: Same as Fig. 7, but this tracked scan has 2 different position in a subscan (when zooming closely one can see 2 faulty dumps at the end of each subscan).