【arcpy】线状要素等距离生成点

客官°小女子只卖身不卖艺 2022-12-17 04:26 131阅读 0赞

基本原理：想要为某个线状要素类中的所有线要素生成等距离节点，可以按照以下步骤实现：

1.  读取要素折点；
2.  结合折点间距离大小以及直线上点与距离关系（通过相似三角形）求得可满足预期距离的点的坐标位置，将所得点坐标信息保存为xls文件；
3.  应用ArcGIS读取xls，生成点状要素类。

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzI2NjQ2MTI5_size_16_color_FFFFFF_t_70_pic_center]  
以下为生成等距离节点xls文件得代码，由于xls最多可存储65535行，本代码会将多余的部分存到同一份xls文件的下一个表中。

# -*- coding: utf-8 -*-
    import sys, math
    import arcpy
    import xlwt
    
    reload(sys)
    sys.setdefaultencoding('utf8')
    
    fc_path = unicode("./xxx.mdb/line", "utf-8")
    
    
    # 根据两点坐标和由一点出发的距离，求第三点坐标
    def calPosition(p1, p2, d):
        p1_x = p1[0]
        p1_y = p1[1]
        p2_x = p2[0]
        p2_y = p2[1]
        d_12 = math.sqrt(math.pow((p2_x - p1_x), 2) + math.pow((p2_y - p1_y), 2))
        d_x = (d * (p2_x - p1_x)) / d_12
        d_y = (d * (p2_y - p1_y)) / d_12
        x = p1_x + d_x
        y = p1_y + d_y
        return (x, y)
    
    
    # 计算一条折线总长度及刨除最后一部分的折线长度
    def calLength(points):
        length_total = 0
        length_exclude_last_segment = 0
        for i in range(0, len(points)-1):
            p1 = points[i]
            p2 = points[i+1]
            p1_x = p1[0]
            p1_y = p1[1]
            p2_x = p2[0]
            p2_y = p2[1]
            d_12 = math.sqrt(math.pow((p2_x - p1_x), 2) + math.pow((p2_y - p1_y), 2))
            length_total += d_12
            if i!= (len(points)-2):
                length_exclude_last_segment += d_12
        return length_total, length_exclude_last_segment
    
    
    # 根据切分距离生成折点
    def splitLine(points, d):
        vertex_generated = [points[0]]
        point_index = 1 # 点集中即将访问的下一个点
        
        # 未遍历完折线所有折点时
        while point_index < len(points):
            points_sub = []
            points_sub.append(vertex_generated[-1])  # 新生成折点作为起点
            d_balance = 0
            point_index_copy = point_index
    
            # 从当前位置向后遍历，在总长度未满足条件前不断添加折点
            for i in range(point_index_copy, len(points)):
                points_sub.append(points[i])
                length_total, length_exclude_last_segment = calLength(points_sub)
    
                # print point_index, length_total, length_exclude_last_segment
                if length_total >= d:
                    d_balance = d - length_exclude_last_segment
                    point_index = i
                    break
                else:
                    point_index = i + 1
            
            # 如果最后一段折线长度大于0，可以排除遍历到最后折点不足情况
            if d_balance > 0:
                p1 = points_sub[-2]
                p2 = points_sub[-1]
                vertex = calPosition(p1, p2, d_balance)
                vertex_generated.append(vertex)
        
        vertex_generated.append((points[-1][0], points[-1][1]))
        # print vertex_generated
        return vertex_generated
        
    
    def addSheet(workbook, n):
        sheet_name = "Sheet" + str(n)
        worksheet = workbook.add_sheet(sheet_name)
        worksheet.write(0, 0, "x")
        worksheet.write(0, 1, "y")
        return worksheet
    
    
    def saveVertex(wooksheet, vertex_generated, vertex_num):
        for i in range(vertex_num, vertex_num + len(vertex_generated)):
            worksheet.write(i, 0, vertex_generated[i-vertex_num][0])
            worksheet.write(i, 1, vertex_generated[i-vertex_num][1])
    
    
    workbook = xlwt.Workbook(encoding='utf-8')
    worksheet = addSheet(workbook, 1)
    vertex_num = 1
    sheet_index = 1
    
    with arcpy.da.SearchCursor(fc_path, ("OID@", "SHAPE@")) as cursor:
        for row in cursor:
            print "------next row------"
    
            for part in row[1]:
                points = []
    
                for point in part:
                    points.append((point.X, point.Y))
    
                vertex_generated = splitLine(points, 10)
                if (vertex_num + len(vertex_generated)) > 65500:
                    vertex_num = 1
                    sheet_index += 1
                    worksheet = addSheet(workbook, sheet_index)
                
                saveVertex(worksheet, vertex_generated, vertex_num)
                vertex_num += len(vertex_generated)
                break
    
    workbook.save('vertex_generated.xls')
    print "------done------"

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2JhaWR1XzI2NjQ2MTI5_size_16_color_FFFFFF_t_70_pic_center]: /images/20221123/9911491cdfb94e30a86882d4d6354214.png