LIDAR数据类似于带有激光的RADAR，是光检测和测距的缩写。
laspy库提供了python API，用于读取，写入和操作一种流行的用来存储LIDAR数据的（.LAS文件）。 LAS文件是根据几种规格打包的二进制文件。
- Las： 二进制格式；是点云lidar数据的一种典型格式。
las文件是根据多种las规格打包而成的二进制文件。
- Las 规格
las1.0支持las1.0~1.2，对格式1.3，1.4提供了初步支持。
| las规格 |
文档 |
| 1.0 |
http://www.asprs.org/a/society/committees/standards/asprs_las_format_v10.pdf |
| 1.1 |
http://www.asprs.org/a/society/committees/standards/asprs_las_format_v11.pdf |
| 1.2 |
http://www.asprs.org/a/society/committees/standards/asprs_las_format_v12.pdf |
| 1.3 |
http://www.asprs.org/a/society/committees/standards/LAS_1_3_r11.pdf |
| 1.4 |
http://www.asprs.org/a/society/committees/standards/LAS_1_4_r11.pdf |
| las1.0~las1.2 |
las1.3~las1.4 |
| 头文件区 |
头文件区 |
| 变长记录区 |
变长记录区 |
| 点数据区 |
点数据区 |
|
波形数据记录区、扩展变长记录区 |
蓝色：las1.3新增头文件区
红色：las1.4新增头文件区
| 属性名 |
laspy缩写 |
文件格式（长度） |
| File Signature |
file_signature |
char[4] (4) |
| File Source Id |
file_source_id |
unsigned short[1] (2) |
| (Reserved or Global Encoding) |
global_encoding |
unsigned short[1] (2) |
| Gps Time Type |
gps_time_type |
Part of Global Encoding |
| Project Id (4 combined fields) |
guid |
ulong+ushort+ushort+char[8] (16) |
| Verion Major |
version_major |
unsigned char[1] (1) |
| Version Minor |
version_minor |
unsigned char[1] (1) |
| Version Major + Minor |
version |
(see above) |
| System Identifier |
system_id |
char[32] (32) |
| Generating Software |
software_id |
char[32] (32) |
| File Creation Day of Year |
(handled internally) |
unsigned short[1] (2) |
| File Creation Year |
(handled internally) |
unsigned short[1] (2) |
| Creation Day + Year |
date |
(see above) |
| Header Size |
header_size |
unsigned short[1] (2) |
| Offset to Point Data |
data_offset |
unsigned long[1] 4 |
| Number of Variable Length Recs |
(handled internally) |
unsigned long[1] 4 |
| Point Data Format Id |
data_format_id |
unsigned char[1] (1) |
| Data Record Length |
data_record_length |
unsigned short[1] (2) |
| Number of point records |
records_count |
unsigned long[1] (4) |
| Number of Points by Return Ct. |
point_return_count |
unsigned long[5 or 7] (20 or 28) |
| Scale Factor (X, Y, Z) |
scale |
double[3] (24) |
| Offset (X, Y, Z) |
offset |
double[3] (24) |
| Max (X, Y, Z) |
max |
double[3] (24) |
| Min (X, Y, Z) |
min |
double[3] (24) |
| Start of waveform data record |
start_waveform_data_rec |
unsigned long long[1] (8) |
| Start of first EVLR |
start_first_evlr |
unsigned long long[1] (8) |
| Number of EVLRs |
(handled internally) |
unsigned long[1] (4) |
| Number of point records |
point_records_count |
unsigned long long[1] (8) |
| Number of points by return ct. |
point_return_count |
unsigned long long[15] (120) |
| LAS Format |
Point Formats Supported |
| 1.0，1.1 |
0, 1 |
| 1.2 |
0, 1, 2, 3 |
| 1.3 |
0, 1, 2, 3, 4, 5 |
| 1.4 |
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 |
| LAS规格 |
支持的点数据格式 |
| 1.0，1.1 |
0,1（x、y、z、intensity、flag_type、raw_classification、user_data、pt_src_id，1新增gps_time） |
| 1.2 |
0, 1, 2, 3（2减少gpsTime，3新增red、green、blue） |
| 1.3 |
0, 1, 2, 3, 4, 5，新增wavefm_packet_desc_index、byte_offset_to_waveform_data等； |
| 1.4 |
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 |
点格式：
| Field Name |
laspy简写 |
File Format[number] (length) |
备注 |
| X |
X (x for scaled) |
long[1] (4) |
|
| Y |
Y (y for scaled) |
long[1] (4) |
|
| Z |
Z (z for scaled) |
long[1] (4) |
|
| Intensity |
intensity |
unsigned short[1] (2) |
|
| (Flag Byte) |
flag_byte |
unsigned byte[1] (1) |
|
| (Classification Byte) |
raw_classification |
unsigned byte[1] (1) |
|
| User Data |
user_data |
unsigned char[1] (1) |
|
| Point Source Id |
pt_src_id |
unsigned short[1] (2) |
|
| GPS Time |
gps_time |
double[1] (8) |
1新增 |
| Red |
red |
unsigned short[1] (2) |
2新增 |
| Green |
green |
unsigned short[1] (2) |
2 新增 |
| Blue |
blue |
unsigned short[1] (2) |
2 新增 |