These basins are evident in the topographic image.

这些盆地在地形图中很明显。

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C or F value, the X and Y coordinates of the center of a pixel at the up-left corner of the image, can be measured according to characteristic point in topographic map.

值为栅格图像左上角像素中心在地图上的X，Y坐标，其值可以根据特征点在地形图中的坐标量测获得。

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This paper discussed in detail algorithm of geometric rectification by scanned topographic map based on teaching model with least squares method to heighten image quality and data accuracy.

针对扫描矢量化这一数据采集手段，以提高图像质量、数据精度为目的，以教学模型为基础，利用最小二乘原理，详细讨论了扫描后的地形图几何纠正算法。

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