AERIAL RECONNAISSANCE FOR TRIANGULATION

Abstract

Since 1929 much of the primary triangulation carried out by the Geodetic Service of Canada has been preceded by an aerial reconnaissance of the areas: during this reconnaissance a tentative selection is made of station sites, and likely lines of sight are indicated. Varied types of topography have been covered—mountainous, rolling, flat wooded, mountain valleys. In most cases there were three common factors: the areas were well watered with lakes and rivers which permitted low flying in safety with pontoonor skii-equipped planes, ground transportation was difficult, and no contour maps existed. In some of the areas existing maps were very incomplete; of a few, reconnaissance aerial maps were available in which the planimetry was good; the better the map the easier the aerial reconnaissance. In all cases it was considered necessary that the air operations be checked by ground visits to the tentatively selected stations.     

AERIAL TRIANGULATION FOR CONTROL PROVISION

The author has been involved in aerial triangulation, in various capacities, for some 27 years. This period has seen some very significant changes worthy of remark. This essay is a general review of that period; it does not go into detail and no formulae are quoted. The idea has been to look at the more notable developments, skipping the earlier and well documented period in favour of more recent times, particularly as regards the references. The objective will have been achieved if it provides a starting point, indicating further reading, for those who wish to study the subject in greater depth.     

THE YELL AERIAL TRIANGULATION EXPERIMENT

The paper considers the experimental comparison of a method of aerial triangulation in previous experimental use by Eden and the standard Ordnance Survey method using stereocomparators. The accuracy of plan fixations was high by both methods, with Eden's method providing the better result. A comparison is made of the times taken under experimental conditions for both methods.     

GPS精密单点定位在空中三角测量中的应用

结合一例带有试验性质的GPS辅助空中三角测量的工程实践,从不同的角度和数据处理方案,分析了GPS精密单点定位结果,结果表明采用GPS精密单点定位辅助空中三角测量的方案不仅可行,而且不需要地面基准站支持,提高了摄影测量效率并可降低测量成本.     

ANALYTICAL AERIAL TRIANGULATION WITH ANGULAR MEASUREMENTS

In recent years interest has been increasing in the use of measurements from single photographs for analytical work. A monocular instrument based on the theodolite is described, together with preliminary test results.     

A SIMPLIFIED ANALYTICAL METHOD FOR THE ADJUSTMENT OF AERIAL TRIANGULATION

Abstract

This method, which has been used in connection with Wild A5 and A6 stereoplotting machines, was developed in an endeavour to retain as many as possible of the advantages of the analytical method without incurring the corresponding disadvantage of excessively lengthy computation. It is capable of being quickly learnt by even an inexperienced computer, and adequate checks on the accuracy of the numerical work are easily applied where not automatically provided. It has the advantage over the graphical method formerly used, that no control point is accepted as more reliable than another, equal weight being given to all, and an indication of the relative reliability of the individual control points is furnished by the table of residual errors obtained.