Table 4. Comparison of 1966 and 1981 area statistics in hectares 
derived from remote sensing and from official farm 
census records for Old Machar Parish. Classes A and Z 
are equivalent to "crops and grass". 
For 1966, the area derived from remote sensing is less than 0.2 percent 
greater than the officially recorded area for crops and grass. For 
1981, the remote sensing data provides a figure which is almost 11.8 
percent greater than the figure from the farm census records. Two 
factors which explain the underestimation in the farm census are: 
(i) After 1970 small holdings involving less than 40 man-days work per 
annum were not recorded. 
(ii) Farm amalgamations have increased greatly since 1966 and may have 
resulted in some land in the parish being owned by farmers residing 
outside the parish. The census would place such land in the parish 
of the farmer's residence. 
The results also reveal a significant increase in the land occupied by 
sand and gravel quarries (Q)—from 55.4 hectares in 1966 to 79.8 
hectares in 1981. This increase is mainly a result of the increasing 
demand for building materials associated with the growing residential 
and commercial/industrial land uses in the parish. Some of the new 
residential developments are mobile home sites adjacent to farms which 
are partly indicative of how inadequately housing demands are met. The 
area occupied by public buildings (B) in the parish has increased— 
largely due to the greater number of schools, including a new high 
school. Transportation routes (T) have also increased—new roads have 
been built and old roads have been widened. 
Of the 190.6 hectares of cropland lost from the 4 NGS area of Old Machar 
which was further analyzed to determine land capability lost, 125.4 
hectares were found to be grade B land and 61 hectares were found to be 
grade B- land. (The remaining 4.2 hectares were unclassified.) 
Table 5 shows the time spent on various phases of the project. Time 
spent interpreting, coding, and inputing data for the second year is 
much less than that for the original survey (over 40 partial or whole 
NGS) since 18 NGS were unchanged and were simply duplicated. The 
boundary maps are, of course, able to be used with any categorical data 
files for the same and adjacent parishes. The total time required to 
interpret and process the data for the 29 km^ of Old Machar Parish for 
two years at the 40m x 50m ground cell size was approximately 68 hours. 
Data types 
1966 land cover 
1981 land cover 
boundary 
Table 5. 
Interpreting 
and coding time 
26 
9 
5 
Inputing to 
computer time 
8 
5 
5.5 
Computer 
processing time 
4.5 
4.5 
Time estimates in hours for interpretation and processing 
of Old Machar data (excluding land capability data).