## Materials and Methods
### Image Analysis  
The TerraSAR-X data were calibrated to \"sigma naught\" (\(\sigma\)0), the radar reflectivity per unit area in ground range using ERDAS Imagine (version 2013-2016), to correct for geometry of acquisition cf. [(28)]. For image interpretation and analysis the intensity images were directly imported into the geographic information system (GIS) of ESRI ArcGIS 10.1 where the data was repetitively verified with geospatial in situ data or compared to monitoring results.  
According to initial tests, statistical analysis of backscatter differences such as height, mean value, amplitude, or variance seemed not sufficient for the clear demarcation of most intertidal  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Site** & **Date** & \begin{tabular}{c} **Image** \\ **Mode** \\ \end{tabular} & \begin{tabular}{c} **Rel.** \\ **Orbit** \\ \end{tabular} & **Inc.** [\({}^{\circ}\)] & \begin{tabular}{c} **Orbit** \\ **Dir.** \\ \end{tabular} & \
\begin{tabular}{c} **A tLT** \\ **[min]** \\ \end{tabular} &
\begin{tabular}{c} **Gauge** \\ **[cm \(<\) NHN]** \\ \end{tabular} & **WS** & **WD** [\({}^{\circ}\)] \\ \hline Norderney & 21/07/2009 & HRS & 131 & 20.8 & A & 63 & 111 2 & 3.9 7 & 60 \\ Juist/Borkum & 05/04/2011 & SM & 63 & 37.4 & D & 9 & 136 1 & 10.9 6 & 210 \\ Spiekeroog & 17/05/2011 & SL & 40 & 37.0 & A & 14 & 142 3 & 7.6 8 & 270 \\ Nordermey & 02/06/2011 & HRS & 116 & 45.1 & A & 11 & 145 2 & 5.4 7 & 360 \\ Nordermey & 04/06/2011 & SL & 139 & 23.3 & D & 0 & 160 2 & 5.5 7 & 60 \\ Nordermey & 16/07/2011 & HS & 116 & 45.1 & A & \(-\)18 & 152 2 & 3.2 7 & 160 \\ Nordermey & 19/07/2011 & SL & 154 & 46.6 & D & \(-\)82 & 106 2 & 5.5 7 & 190 \\ Nordermey & 14/10/2011 & SL & 139 & 23.6 & D & 15 & 174 2 & 3.2 7 & 130 \\ Nordermey & 10/01/2012 & HRS & 139 & 23.5 & D & 43 & 116 2 & 3.6 7 & 270 \\ Wangeroog & 19/05/2012 & SL & 116 & 47.9 & A & 50 & 144 5 & 4.8 8 & 30 \\ Baltrum & 07/06/2012 & SL & 63 & 35.3 & D & \(-\)52 & 144 4 & 3.1 7 & 150 \\ Wangeroog & 15/10/2012 & HRS & 40 & 38.1 & A & \(-\)2 & 142 4 4 & 6.2 8 & 160 \\ Nordermey & 30/11/2012 & SL & 63 & 36.4 & D & 21 & 129 2 & 5.4 7 & 10 \\ Nordermey & 09/06/2013 & HRS & 131 & 21.1 & A & \(-\)23 & 144 2 & 6.9 7 & 360 \\ Nordermey & 28/02/2014 & HRS & 131 & 21.1 & A & 63 & 67 2 & 3.4 7 & 60 \\ Nordermey & 14/06/2014 & HRS & 63 & 36.1 & D & 46 & 132 2 2 & 9.9 7 & 350 \\ Nordermey & 11/08/2014 & HRS & 116 & 45.1 & A & 6 & 111 2 & 8.5 7 & 220 \\ Nordermey & 07/12/2014 & HRS & 63 & 36.1 & D & 56 & 102 2 & 7.6 7 & 190 \\ Nordermey & 19/04/2015 & HRS & 78 & 54.3 & D & 40 & 166 2 & 2.9 7 & 260 \\ Langeoog & 21/06/2016 & HRS & 78 & 54.2 & D & 26 & 105 2 & 2.5 7 & 310 \\ \hline \hline \end{tabular}  
* Water level data (source: Federal Waterways and Shipping Administration WSV, provided by Federal Institute for Hydrology BFO) are from the gauges: 1: Borkum Fischerbaje, 2 Nordermey Riffgat, 3 Spiekeroog, 4 Wangerooge West, and 5 Wingeroog East. Wind speed and wind direction (source: German Weather Service DWD) are from the weather stations: 6 Borkum, 7 Nordermey, and 8 Spiekeroog.  
\end{table}
Table 1: TerraSAR-X acquisitions used in this study. Image mode: HRS = High Resolution Spotlight, SL = Spotlight, SM = Stripmap, Inc. = Incidence angle, Orbit direction: A = ascending, D = descending, \(\Delta\) tLT = Acquisition time related to low tide (_positive values_: acquisition at rising tide), Gauge level related to normal height null (NHN), WS, WD = wind speed, wind direction.  
surfaces. Therefore, in this study the images are analyzed via visual interpretation integrating i.a. the patterns of internal structures or textures characterizing the surface structures reflected by TerraSAR-X data as well as contextual data including extensive in situ data or weather and gauge level data (cf. Introduction).