中央子午线

本文通过拉萨&贡嘎、GPS控制网的研究，根据地理位置不同，选择合适的中央子午线和基准投影面，是抵御长度变形的有效手段；

According to the research on the GPS control nets in LASA , the conclusion is that it is an effective way to control the length deformation through choosing a proper central meridian and basic project plane according to the different location is generated .

城市独立坐标系下似中央子午线的确定

The Calculation of the Approximately Central Meridian in the Urban Independent Coordinate System

关于抵偿高程面与移动中央子午线最佳选取问题的研究

Study on the Optimal Selection of the Compensating Level Surface and Moving Middle Meridian

方法三：基于平差软件的自定义坐标系统，采用任意中央子午线下测区平均高程面为投影面。

Method three is , based on self-defining coordinate system of adjustment software , to take survey field average height as projection plane of option central meridian .

论述了建立独立坐标系时中央子午线及投影面的选择与各地区投影长度变形值的关系，说明了尽量利用原有坐标系统的重要性。

The relation between central meridian projection plane choice and the distortion value of projection length of areas was discoursed on , and then the essentiality to make use of intrinsic coordinate system was explained .

用于投影的抵偿面是计算对象所在的平均高程面，用于投影的中央子午线是计算对象所在的平均经线，因此计算结果最接近实测值。

In this model , the compensation projection plane is the surface of average elevation of calculated objects , and the central meridian of projection is the average longitude line of calculated objects , so the calculating result is most close to the real surveying value .

方法标记植孔中央所在的子午线及在该子午线上植孔外缘与角膜缘的距离（两点标记法）；

Methods Marks were made on the meridian where the center of recipient bed was located , and at that meridian the distance between the external edge of recipient bed and the limbus ( two point marking technique ) was also marked .