如何讲好《测量学》的绪论课

如何讲好《测量学》的绪论课郑国忠（清华大学）一、《测量学》教师的责任１９９２年中国测绘学会非测绘专业《测量学》教学委员会在重庆召开的《测量学》教学研讨会上组织了青年教师结论课的讲课评议，并决定１９９４年于北京开展青年教师绪论课讲课竞赛，这是培养青年教...     

研究波罗的海海平面的GPS项目

为了研究波罗的海海平面的变化以及统一波岁的海沿岸各国的高程系统，于1990年秋天，在波罗的海地区进行了为时两周的GPS会战。来自丹麦、芬兰、德国、波兰和瑞典各方在沿着波罗的海的26个验潮器以及8个VLBI和SLR基准站上进行了GPS观测，其基线长度范围从230Km到1600Km。观测值使用伯尔尼3．3版本软件，应用了轨道改进技术，以同的模式进行处理。为了摆脱来自单频数据电离层折射所引入的比例误差的影响，使用L4观测值来估计电离层的当地模型。考虑了对流层天顶改正数。初步结果表明，在ITRF89系统上，相对于波茨坦SLR站，其水平位置中误差（RMS）的平均值约为±3cm，坚向位置的为±7cm。使用水准测量高程将GPS结果变换为大地水准面高度以后，和使用最小二乘改进的司托克斯公式（LSMS）、改良的莫洛金斯基及NKG斯堪的纳维亚大地水准面1989（NKG－89）模型计算得的重力测量大地水准面高度进行绝对比较，给出差数的标准偏差值为：对于NKG－89模型为±7cm到±9cm，对于LSMS模型和改良的莫洛金斯基模型为±9cm到±30cm。发现瑞典高程系比波罗的海其他国家的高程系，对于NKG－89模型来说，约高出8～37cm。     

SA对GPS静态相对定位的影响

我们对在ＧＰＳ卫星上实施“选择用户”（ＳＡ）对南加州常设ＧＰＳ大地测量阵（ＰＧＧＡ）测站的日常相对定位的影响，已进行了实验检测。ＰＧＧＡ于１９９０年２月开始工作。日常数据采集由Ｓｃｒｉｐｐｓ海洋学研究所（ＳＩＯ）和喷气推进实验室（ＪＰＬ）从设置在ＪＰＬ，ＳＩＯ和ＰｉｎｏｎＦｌａｔ观测站的三台Ｒｏｇｕｅ ＳＮＲ－８接收机，以及设置在加利福尼亚，马萨诸塞和佛罗里达的ＣＩＧＮＥＴ踊跟踪站的上的三台Ｍｉｎ     

An evaluation of marine bird population trends following the Exxon Valdez oil spill, Prince William Sound, Alaska

We examined post-spill trends (1989-1998) of marine bird populations in Prince William Sound (PWS) following the Exxon Valdez oil spill (EVOS) to evaluate recovery of injured taxa. Two criteria were employed. First, we examined population trends of injured taxa only in the oiled area of PWS using regression models. Second, we examined population trends of injured taxa in the oiled area relative to the unoiled area using homogeneity of the slopes tests. We considered a population recovering if there was a positive trend using either criteria. We considered a population not recovering if there was no trend using either criteria or a negative trend in the oiled area. A significant negative trend in the oiled area relative to the unoiled area was considered a continuing and increasing effect. Most taxa for which injury was previously demonstrated were not recovering and some taxa showed evidence of increasing effects nine years after the oil spill. Four taxa (loons Gavia spp, Harlequin Duck Histrionicus histrionicus, Bufflehead Bucephala spp, and North-western Crow Corvus caurinus) showed weak to very weak evidence of recovery. None of these taxa showed positive trends in both winter and summer. Nine taxa (grebes Podiceps spp, cormorants Phalacrocorax spp, Black Oystercatcher Haematopus bachmani, Mew Gull Larus canus, Glaucous-winged Gull Larus glaucescens, terns Sterna spp, murres Uria spp, Pigeon Guillemot Cepphus columba, and murrelets Brachyramphus spp) showed no evidence of recovery during summer or winter. Four taxa (scoters Melanitta spp, mergansers Mergus spp, goldeneyes Bucephala spp, and Black-legged Kittiwaka Rissa tridactyla) showed evidence of continuing, increasing effects. We showed evidence of slow recovery, lack of recovery, and divergent population trends in many taxa which utilize shoreline and nearshore habitats where oil is likely to persist. Potential lingering spill effects and natural variability appear to be acting in concert in delaying recovery of many PWS bird populations.     

一种新的GPS无线电探空测风系统

一种新的ＧＰＳ无线电探空测风系统ＤａｖｉｄＢ．Ｃａｌｌ（美国大气仪器研究公司）１引言ＧＰＳ－７００是一种新的无线电探空测风系统，用来测量大气压力、温度、湿度（ＭＥＴ资料）及风向风速。这种ＧＰＳｏｎｄｅ＂（无线电探空仪）用转换后的ＧＰＳ（全球定位系统）...