RTCM协议
RTCM(Radio Technical Commission for Maritime Services)是一个非营利性组织，致力于制定和推广用于导航和定位的标准。RTCM协议最初用于海事服务，后来扩展到广泛的GNSS应用领域。RTCM协议的主要目的是提高GNSS数据的传输效率和定位精度。
RTCM官网链接如下：Home
RTCM最新协议是由国际海运事业无线电技术委员会(Radio Technical Commission for Maritime services)制定的RTCM SC10403.3协议，简称RTCM 3.3协议，可为卫星导航系统中的移动站提供差分改正数据，提高其定位精度。
RTCM定义的内容包括卫星导航数据的头文件，信息长度，如何解码，如何编码，各个GNSS的系统如何分配数据长度，数据位置，各种信息的定义。正因为都是遵循这个协议，所以不管是什么导航厂家，都可以接收到来自北斗，GPS，Galileo，GLONASS以及各类增强服务等信息并加以利用。
RTCM主要电文
RTCM 3 M essage s :
RTCM 1001 - L1-Only GPS RTK Observables
RTCM 1002 - Extended L1-Only GPS RTK Observables
RTCM 100 3 - L1&L2 GPS RTK Observables
RTCM 1004 - Extended L1&L2 GPS RTK Observables
RTCM 1005 - Stationary RTK Reference Station ARP
RTCM 1006 - Stationary RTK Reference Station ARP with Antenna Height
RTCM 100 7 - Antenna Descriptor
RTCM 100 8 - Antenna Descriptor and Serial Number
RTCM 100 9 - L1-Only GLONASS RTK Observables
RTCM 1010 - Extended L1-Only GLONASS RTK Observables
RTCM 101 1 - L1&L2 GLONASS RTK Observables
RTCM 101 2 - Extended L1&L2 GLONASS RTK Observables
RTCM 101 3 - System Parameters
RTCM 101 5 - Network RTK (MAC), GPS Ionospheric Correction Differences
RTCM 101 6 - Network RTK (MAC), GPS Geometric Correction Differences
RTCM 101 7 - Network RTK (MAC), GPS Combined Geometric and Ionospheric Correction Differences
RTCM 101 9 - GPS Satellite Ephemeris Data
RTCM 10 20 - Glonass Satellite Ephemeris Data
RTCM 10 21 - Helmert-Abridged Molodenski Transformation Parameters
RTCM 10 22 - Molodenski-Badekas Transformation Parameters
RTCM 10 23 - Residuals, Ellipsoidal Grid Representation
RTCM 10 24 - Residuals, Plane Grid Representation
RTCM 10 25 - Projection Parameters, Projection Types other than Lambert Conic Conformal (2 SP) and Oblique Mercator
RTCM 10 26 - Projection Parameters, Projection Type LCC2SP (Lambert Conic Conformal (2 SP))
RTCM 10 27 - Projection Parameters, Projection Type OM (Oblique Mercator)
RTCM 10 29 - Unicode Text String
RTCM 1033- Receiver and Antenna descriptors
RTCM 103 7 - Network RTK (MAC), GLONASS Ionospheric Correction Differences
RTCM 103 8 - Network RTK (MAC), GLONASS Geometric Correction Differences
RTCM 103 9 - Network RTK (MAC), GLONASS Combined Geometric and Ionospheric Correction Differences
RTCM 10 42 - BDS Satellite Ephemeris Data
RTCM 10 44 - QZSS Satellite Ephemeris Data
RTCM 10 45 - Galileo F/NAV Satellite Ephemeris Data
RTCM 10 46 - Galileo I/NAV Satellite Ephemeris Data
RTCM 1230 - GLONASS L1&L2 Code-Phase Biases
RTCM 3 MSM messages:
RTCM1071 GPS MSM1 - Compact Pseudoranges
RTCM1072 GPS MSM2 - Compact PhaseRanges
RTCM1073 GPS MSM3 - Compact Pseudoranges and PhaseRanges
RTCM1074 GPS MSM4 - Full Pseudoranges and PhaseRanges plus CNR
RTCM1075 GPS MSM5 - Full Pseudoranges, PhaseRanges, PhaseRangeRate and CNR
RTCM1076 GPS MSM6 - Full Pseudoranges and PhaseRanges plus CNR (high resolution)
RTCM1077 GPS MSM7 - Full Pseudoranges, PhaseRanges, PhaseRangeRate and CNR (high resolution)
RTCM1081 GLONASS MSM1 - Compact Pseudoranges
RTCM1082 GLONASS MSM2 - Compact PhaseRanges
RTCM1083 GLONASS MSM3 - Compact Pseudoranges and PhaseRanges
RTCM1084 GLONASS MSM4 - Full Pseudoranges and PhaseRanges plus CNR
RTCM1085 GLONASS MSM5 - Full Pseudoranges, PhaseRanges, PhaseRangeRate and CNR
RTCM1086 GLONASS MSM6 - Full Pseudoranges and PhaseRanges plus CNR (high resolution)
RTCM1087 GLONASS MSM7 - Full Pseudoranges, PhaseRanges, PhaseRangeRate and CNR (high resolution)
RTCM1091 GALILEO MSM1 - Compact Pseudoranges
RTCM1092 GALILEO MSM2 - Compact PhaseRanges
RTCM1093 GALILEO MSM3 - Compact Pseudoranges and PhaseRanges
RTCM1094 GALILEO MSM4 - Full Pseudoranges and PhaseRanges plus CNR
RTCM1095 GALILEO MSM5 - Full Pseudoranges, PhaseRanges, PhaseRangeRate and CNR
RTCM1096 GALILEO MSM6 - Full Pseudoranges and PhaseRanges plus CNR (high resolution)
RTCM1097 GALILEO MSM7 - Full Pseudoranges, PhaseRanges, PhaseRangeRate and CNR (high resolution)
RTCM1101 SBAS MSM1 - Compact Pseudoranges
RTCM1102 SBAS MSM2 - Compact PhaseRanges
RTCM1103 SBAS MSM3 - Compact Pseudoranges and PhaseRanges
RTCM1104 SBAS MSM4 - Full Pseudoranges and PhaseRanges plus CNR
RTCM1105 SBAS MSM5 - Full Pseudoranges, PhaseRanges, PhaseRangeRate and CNR
RTCM1106 SBAS MSM6 - Full Pseudoranges and PhaseRanges plus CNR (high resolution)
RTCM1107 SBAS MSM7 - Full Pseudoranges, PhaseRanges, PhaseRangeRate and CNR (high resolution)
RTCM1111 QZSS MSM1 - Compact Pseudoranges
RTCM1112 QZSS MSM2 - Compact PhaseRanges
RTCM1113 QZSS MSM3 - Compact Pseudoranges and PhaseRanges
RTCM1114 QZSS MSM4 - Full Pseudoranges and PhaseRanges plus CNR
RTCM1115 QZSS MSM5 - Full Pseudoranges, PhaseRanges, PhaseRangeRate and CNR
RTCM1116 QZSS MSM6 - Full Pseudoranges and PhaseRanges plus CNR (high resolution)
RTCM1117 QZSS MSM7 - Full Pseudoranges, PhaseRanges, PhaseRangeRate and CNR (high resolution)
RTCM1121 BEIDOU MSM1 - Compact Pseudoranges
RTCM1122 BEIDOU MSM2 - Compact PhaseRanges
RTCM1123 BEIDOU MSM3 - Compact Pseudoranges and PhaseRanges
RTCM1124 BEIDOU MSM4 - Full Pseudoranges and PhaseRanges plus CNR
RTCM1125 BEIDOU MSM5 - Full Pseudoranges, PhaseRanges, PhaseRangeRate and CNR
RTCM1126 BEIDOU MSM6 - Full Pseudoranges and PhaseRanges plus CNR (high resolution)
RTCM1127 BEIDOU MSM7 - Full Pseudoranges, PhaseRanges, PhaseRangeRate and CNR (high resolution)
RTCM版本历史
RTCM2.X：只支持部分系统，进行单一功能的扩展，目前该格式使用的已经不多；
RTCM3.0： 表示从 RTCM2.X 向 RTCM3.X 进行过渡，目前使用的并不多；
RTCM3.2： 使用的较多，为标准格式；
RTCM3.3： 格式与 RTCM3.2 基本一致，在RTCM3.2基础上增加了北斗星历、GA1-7星历、SBAS系统等；
RTCM数据格式
RTCM数据格式分为包头、有效数据、校验帧尾
包头：
前导码：以 D3 00开头；
保留位：保留位补0, 存在6个二进制位；
电文长度：电文的有效数据长度；
RTCM常用的电文类型
观测值电文：单个卫星系统为1包电文，所以多系统的单个历元中会存在多条电文；
星历电文：单颗卫星的信息为1包电文，电文在有卫星信息更新的时候进行播发，不同的卫星系统星历更新的时间段不一样；
基站电文：基站坐标、基站天线信息、辅助信息等；
SSR电文：精密轨道、精密钟差；