發(fā)布時(shí)間：2018-12-11 20:20

【摘要】：隨著氣候變暖和極端天氣增多,冰雪制圖和雪災(zāi)評(píng)估成為全球研究的熱點(diǎn)。合成孔徑雷達(dá)(SAR)具有全天候、全天時(shí)、高分辨率的特點(diǎn),在積雪制圖研究中有著特殊的優(yōu)勢(shì),彌補(bǔ)光學(xué)衛(wèi)星的不足。本文的主要研究?jī)?nèi)容為利用SAR圖像提取積雪覆蓋面積,并對(duì)提取結(jié)果進(jìn)行驗(yàn)證分析。合成孔徑雷達(dá)干涉(InSAR)技術(shù),可用于地表相干性評(píng)估。本文選取了不同地區(qū)、不同地形、不同時(shí)間段的多組ERS-1/2串接干涉數(shù)據(jù)對(duì),統(tǒng)計(jì)分析雪及其它地物的相干性。結(jié)果表明,對(duì)于時(shí)間基線為一天的干涉對(duì),積雪、水域、冰面、森林等地物相干值較低,而其它地物的相干值相對(duì)較高。本文還利用ERS-2和ASAR六組時(shí)間基線較長(zhǎng)的干涉對(duì),分析普莫雍錯(cuò)湖地區(qū)地物的相干性。與時(shí)間間隔僅一天的相干性對(duì)比發(fā)現(xiàn),地物在間隔35天和70天的相干性下降明顯。本文根據(jù)積雪與其它地物的相干性差異,采取相干性閾值分類的方法,提取了多組實(shí)驗(yàn)地區(qū)的積雪覆蓋面積。將SAR圖像積雪提取結(jié)果與同時(shí)期的光學(xué)圖像積雪分類結(jié)果對(duì)比,計(jì)算積雪提取的準(zhǔn)確度,并分析錯(cuò)誤分類的原因。實(shí)驗(yàn)表明,InSAR技術(shù)可以有效地提取積雪面積信息。時(shí)間基線較短的干涉對(duì),有利于提高積雪面積的提取精度。然而這種方法需要實(shí)驗(yàn)地區(qū)的先驗(yàn)信息,如氣候、地形等,同時(shí)復(fù)雜地表對(duì)積雪提取精度影響較大。本文還分析了SAR圖像疊掩和陰影對(duì)積雪分類的影響,加入了疊掩和陰影區(qū)的判別。結(jié)果表明,因雪山的疊掩和陰影區(qū)也可能有積雪覆蓋,若直接排除這類區(qū)域,并不能明顯地提高分類精度。論文的最后一章,InSAR技術(shù)用于城鎮(zhèn)地區(qū)的積雪檢測(cè)。利用無雪和有雪時(shí)期多組ASAR數(shù)據(jù),統(tǒng)計(jì)了烏魯木齊地區(qū)的地物相干性。通過分析兩組夏季時(shí)期的干涉對(duì),發(fā)現(xiàn)城鎮(zhèn)由于人類活動(dòng)、農(nóng)作物生長(zhǎng)等因素,35天時(shí)間間隔的相干性非常低,但機(jī)場(chǎng)、大面積廣場(chǎng)等特殊地物的相干性較高。本文還利用四組降雪期的干涉對(duì)、以及一組有雪和無雪的干涉對(duì),分析降雪后城鎮(zhèn)各類地物的相干性變化。結(jié)果表明無雪時(shí)相干性較高的機(jī)場(chǎng)、郊區(qū)荒地,在被積雪覆蓋后相干性顯著下降�？梢岳贸擎�(zhèn)中這類特殊地物的相干性特征判斷是否有雪,進(jìn)而再進(jìn)行積雪覆蓋監(jiān)測(cè)。
[Abstract]:With the increase of climate warming and extreme weather, ice mapping and snow disaster assessment have become the focus of global research. Synthetic Aperture Radar (SAR) has the characteristics of all-weather, all-day and high-resolution, so it has special advantages in snow mapping and makes up for the shortage of optical satellite. The main research content of this paper is to use SAR image to extract snow cover area and verify the result. Synthetic Aperture Radar (SAR) interferometric (InSAR) technique can be used to evaluate surface coherence. In this paper, the coherence of snow and other ground objects is statistically analyzed by selecting multiple sets of ERS-1/2 interference data pairs in different regions, different terrain and different time periods. The results show that the coherence values of snow, water, ice, forest and other ground objects are lower than those of other ground objects when the time baseline is one day. In this paper, the coherence of the features in Pumoyuncao Lake area is analyzed by using six groups of ERS-2 and ASAR interference pairs with long time baselines. Compared with the coherence of only one day, it was found that the coherence between 35 days and 70 days was obviously decreased. According to the difference of the coherence between snow cover and other ground objects, the snow cover area of many experimental areas was extracted by using the method of coherence threshold classification. The results of snow extraction from SAR images are compared with those of optical images in the same period, the accuracy of snow extraction is calculated, and the causes of false classification are analyzed. Experimental results show that InSAR can effectively extract snow area information. The interference pair with shorter time baseline is helpful to improve the accuracy of snow area extraction. However, this method requires prior information such as climate, topography and so on in the experimental area, and the complex surface has a great influence on the accuracy of snow extraction. In this paper, we also analyze the influence of SAR image overlay and shadow on snow classification, and add the discriminant between overlay and shadow region. The results show that snow cover may also exist in the overlay and shadow areas of the snow-covered mountains, and the classification accuracy can not be improved obviously if these areas are excluded directly. In the last chapter, InSAR technology is used to detect snow cover in urban areas. Based on the ASAR data of non-snow and snow-free periods, the coherence of features in Urumqi was analyzed. By analyzing the interference pairs of the two groups in summer, it is found that due to human activities, crop growth and other factors, the coherence of 35 days interval is very low, but the coherence of special features such as airports and large square is high. In this paper, four sets of interference pairs during snowfall period and one pair of interference pairs with and without snow are used to analyze the coherence changes of various features in cities and towns after snowfall. The results showed that the coherence of the airport and the suburban wasteland decreased significantly after snow cover in the absence of snow. It can be used to judge whether there is snow or not and then to monitor the snow cover by using the coherence characteristics of such special features in cities and towns.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN957.52

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 曾琪明,焦健;合成孔徑雷達(dá)遙感原理及應(yīng)用簡(jiǎn)介(三)[J];遙感信息;1998年02期

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本文編號(hào)：2373162