联合GRACE/GOCE重力场模型和GPS/水准数据确定我国85高程基准重力位

GRACE、GOCE卫星重力计划的实施,对确定高精度重力场模型具有重要贡献。联合GRACE、GOCE卫星数据建立的重力场模型和我国均匀分布的649个GPS/水准数据可以确定我国高程基准重力位,但我国高程基准对应的参考面为似大地水准面,是非等位面,将似大地水准面转化为大地水准面后确定的大地水准面重力位为62 636 854.395 3m~2s~(-2),为提高高阶项对确定大地水准面的贡献,利用高分辨率重力场模型EGM2008扩展GRACE/GOCE模型至2190阶,同时将重力场模型和GPS/水准数据统一到同一参考框架和潮汐系统,最后利用扩展后的模型确定的我国大地水准面重力位为62 636 852.751 8m~2s~(-2)。其中组合模型TIM_R4+EGM2008确定的我国85高程基准重力位值62 636 852.704 5m~2s~(-2)精度最高。重力场模型截断误差对确定我国大地水准面的影响约16cm,潮汐系统影响约4~6cm。

Evaluation of the Geopotential Value for the Local Vertical Datum of China Using GRACE/GOCE GGMs and GPS/Leveling Data

The main purpose of this paper is to estimate the zero height geopotential value for the China Local Vertical Datum.The method used is based on a gravimetric approach and benefits from the significant improvements in the determination of the global gravity field by the recent satellite gravity missions such as GRACE and GOCE.The performance of GOCE-based or GRACE/GOCE-based Global Geopotential Models (GGMs) is assessed for estimation of geopotential of the regional vertical datum of China using the GPS/Levelling BMs (benchmarks) from vertical control network.We should conver the normal height to orthometric height.From the evaluation with the GPS/Levelling BMs, it is concluded that the GOCE-based or GRACE/GOCE-based GGMs provide an absolute accuracy at of 40cm, up to their maximum degree and order.Factors that affect the geopotential value of vertical datum include the GOCE commission and omission errors.Among these factors, the effect of the GOCE omission error is investigated by extending the models with the high resolution gravity field model EGM2008.When extending the GOCE-based or GRACE/GOCE-based models with the high resolution gravity field model EGM2008, we should provide the same parameters.At the same time we should unify the frame and tide system between the GGMs and GPS/Levelling dataset.The result shows that, the effect of the GOCE omission error is at the level of 1.6 m2s-2 (about 16 cm), in China, is at decimetre-level when computing local vertical datum geopotential, the effect of the tide system is about 4-6cm.The vertical datum geopotential of China is estimated as 62 636 852.704 5 m2s-2.