title: How to organize/analyze location data based on movement between two geographic polygons?
body: <p>I have a small dataframe which contains points of two polygons on either side of my study system and are pictured below (East in blue West in red). Here is the dataframe. </p>
  
  <pre><code>structure(list(Shore = structure(c(2L, 2L, 2L, 2L, 2L, 2L, 2L, 
  2L, 2L, 2L, 2L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
  1L), .Label = c("East", "West"), class = "factor"), Lat = c(72.45604629, 
  72.44350398, 72.41516226, 72.36734761, 72.33600228, 72.31760236, 
  72.29050994, 72.26066187, 72.2680832, 72.47144353, 72.45604629, 
  72.45604629, 72.44816356, 72.37238665, 72.24127983, 72.26066187, 
  72.29050994, 72.31760236, 72.33600228, 72.36734761, 72.41516226, 
  72.44350398, 72.45604629, 72.45604629), Long = c(-80.89019727, 
  -80.91753044, -80.9496172, -81.0363703, -81.1243118, -81.15639857, 
  -81.16947095, -81.27702103, -81.33465836, -80.90326966, -80.89019727, 
  -80.89019727, -80.84860332, -80.94367521, -81.28474562, -81.27702103, 
  -81.16947095, -81.15639857, -81.1243118, -81.0363703, -80.9496172, 
  -80.91753044, -80.89019727, -80.89019727)), class = "data.frame", row.names = c(NA, 
  -24L))
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/k71MO.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/k71MO.jpg" alt="enter image description here"></a></p>
  
  <p>I also have a dataframe of animal movements which are detected at each of the dots shown in the map. What I want to know is when and where within the system, animals crossed over from red to blue and vice versa. Below is a small section of my data. All data should fall within one of the two polygons (red or blue). The ID column is individual animal ID and the Station column indicates which receiver (A being most northern and 1 most western). I guess in the end I'd be looking for a new dataframe with columns showing the date/time these events happened, the stations the movement occurred on, and the individual that moved.</p>
  
  <pre><code>structure(list(DateTime = structure(c(1503006715, 1503006880, 
  1503007037, 1503007108, 1503007185, 1503007255, 1503007331, 1503007399, 
  1503007554, 1503007633, 1503007709, 1503007775, 1503007845, 1503007987, 
  1503008057, 1503008132, 1503008199, 1503008269, 1503008392, 1503008412, 
  1503008544, 1503008620, 1503009148, 1503009217, 1503009291, 1503009356, 
  1503009376, 1503009421, 1503009488, 1503009508, 1503009558, 1503009578, 
  1503009634, 1503009702, 1503009722, 1503009774, 1503009854, 1503009875, 
  1503009932, 1503010003, 1503010023, 1503010081, 1503010101, 1503010153, 
  1503010234, 1503010254, 1503010312, 1503010332, 1503010383, 1503010463, 
  1503010483, 1503010538, 1503015897, 1503015963, 1503016024, 1503016873, 
  1503017027, 1503017229, 1503022094, 1503022380, 1503022393, 1503022476, 
  1503022559, 1503022641, 1503022721, 1503022785, 1503022798, 1503022855, 
  1503022868, 1503022931, 1503022944, 1503023000, 1503023013, 1503023073, 
  1503023086, 1503023155, 1503023168, 1503023235, 1503023313, 1503023383, 
  1503023397, 1503023461, 1503023474, 1503023533, 1503023612, 1503023625, 
  1503023686, 1503023816, 1503024252, 1502754012, 1502754224, 1502754364, 
  1502754444, 1502754588, 1502754661, 1502754742, 1502754822, 1502758872, 
  1502758944, 1502758971), class = c("POSIXct", "POSIXt"), tzone = "America/New_York"), 
      ID = c(1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 
      1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 
      1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 
      1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 
      1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 
      1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 
      1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 
      1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 
      1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 
      1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 1657L, 
      1658L, 1658L, 1658L, 1658L, 1658L, 1658L, 1658L, 1658L, 1658L, 
      1658L, 1658L), Station = c("TRD1", "TRD1", "TRD1", "TRD1", 
      "TRD1", "TRD1", "TRD1", "TRD1", "TRD1", "TRD1", "TRD1", "TRD1", 
      "TRD1", "TRD1", "TRD1", "TRD1", "TRD1", "TRD1", "TRD2", "TRD1", 
      "TRD2", "TRD2", "TRD2", "TRD2", "TRD2", "TRD2", "TRD1", "TRD2", 
      "TRD2", "TRD1", "TRD2", "TRD1", "TRD2", "TRD2", "TRD1", "TRD2", 
      "TRD2", "TRD1", "TRD2", "TRD2", "TRD1", "TRD2", "TRD1", "TRD2", 
      "TRD2", "TRD1", "TRD2", "TRD1", "TRD2", "TRD2", "TRD1", "TRD2", 
      "TRE5", "TRE5", "TRE4", "TRE4", "TRE4", "TRE4", "TRF3", "TRF4", 
      "TRF3", "TRF3", "TRF3", "TRF3", "TRF3", "TRF4", "TRF3", "TRF4", 
      "TRF3", "TRF4", "TRF3", "TRF4", "TRF3", "TRF4", "TRF3", "TRF4", 
      "TRF3", "TRF4", "TRF4", "TRF4", "TRF3", "TRF4", "TRF3", "TRF4", 
      "TRF4", "TRF3", "TRF4", "TRF4", "TRF4", "TRD1", "TRD1", "TRD1", 
      "TRD1", "TRD1", "TRD1", "TRD1", "TRD1", "TRE2", "TRE2", "TRE1"
      ), Latitude = c(72.35019, 72.35019, 72.35019, 72.35019, 72.35019, 
      72.35019, 72.35019, 72.35019, 72.35019, 72.35019, 72.35019, 
      72.35019, 72.35019, 72.35019, 72.35019, 72.35019, 72.35019, 
      72.35019, 72.34705, 72.35019, 72.34705, 72.34705, 72.34705, 
      72.34705, 72.34705, 72.34705, 72.35019, 72.34705, 72.34705, 
      72.35019, 72.34705, 72.35019, 72.34705, 72.34705, 72.35019, 
      72.34705, 72.34705, 72.35019, 72.34705, 72.34705, 72.35019, 
      72.34705, 72.35019, 72.34705, 72.34705, 72.35019, 72.34705, 
      72.35019, 72.34705, 72.34705, 72.35019, 72.34705, 72.32009, 
      72.32009, 72.32195, 72.32195, 72.32195, 72.32195, 72.29368, 
      72.29111, 72.29368, 72.29368, 72.29368, 72.29368, 72.29368, 
      72.29111, 72.29368, 72.29111, 72.29368, 72.29111, 72.29368, 
      72.29111, 72.29368, 72.29111, 72.29368, 72.29111, 72.29368, 
      72.29111, 72.29111, 72.29111, 72.29368, 72.29111, 72.29368, 
      72.29111, 72.29111, 72.29368, 72.29111, 72.29111, 72.29111, 
      72.35019, 72.35019, 72.35019, 72.35019, 72.35019, 72.35019, 
      72.35019, 72.35019, 72.32544, 72.32544, 72.32738), Longitude = c(-81.09397, 
      -81.09397, -81.09397, -81.09397, -81.09397, -81.09397, -81.09397, 
      -81.09397, -81.09397, -81.09397, -81.09397, -81.09397, -81.09397, 
      -81.09397, -81.09397, -81.09397, -81.09397, -81.09397, -81.08279, 
      -81.09397, -81.08279, -81.08279, -81.08279, -81.08279, -81.08279, 
      -81.08279, -81.09397, -81.08279, -81.08279, -81.09397, -81.08279, 
      -81.09397, -81.08279, -81.08279, -81.09397, -81.08279, -81.08279, 
      -81.09397, -81.08279, -81.08279, -81.09397, -81.08279, -81.09397, 
      -81.08279, -81.08279, -81.09397, -81.08279, -81.09397, -81.08279, 
      -81.08279, -81.09397, -81.08279, -81.11921, -81.11921, -81.13219, 
      -81.13219, -81.13219, -81.13219, -81.16389, -81.16127, -81.16389, 
      -81.16389, -81.16389, -81.16389, -81.16389, -81.16127, -81.16389, 
      -81.16127, -81.16389, -81.16127, -81.16389, -81.16127, -81.16389, 
      -81.16127, -81.16389, -81.16127, -81.16389, -81.16127, -81.16127, 
      -81.16127, -81.16389, -81.16127, -81.16389, -81.16127, -81.16127, 
      -81.16389, -81.16127, -81.16127, -81.16127, -81.09397, -81.09397, 
      -81.09397, -81.09397, -81.09397, -81.09397, -81.09397, -81.09397, 
      -81.15897, -81.15897, -81.17314)), row.names = c(41276L, 
  41277L, 41278L, 41279L, 41280L, 41281L, 41282L, 41283L, 41284L, 
  41285L, 41286L, 41287L, 41288L, 41289L, 41290L, 41291L, 41292L, 
  41293L, 41294L, 41295L, 41296L, 41297L, 41298L, 41299L, 41300L, 
  41301L, 41302L, 41303L, 41304L, 41305L, 41306L, 41307L, 41309L, 
  41310L, 41311L, 41312L, 41313L, 41314L, 41315L, 41316L, 41317L, 
  41318L, 41319L, 41320L, 41323L, 41324L, 41326L, 41328L, 41329L, 
  41330L, 41331L, 41332L, 41432L, 41433L, 41434L, 41436L, 41437L, 
  41438L, 41441L, 41447L, 41448L, 41452L, 41454L, 41458L, 41460L, 
  41463L, 41464L, 41465L, 41466L, 41467L, 41469L, 41471L, 41472L, 
  41474L, 41475L, 41476L, 41477L, 41478L, 41479L, 41480L, 41481L, 
  41482L, 41483L, 41484L, 41485L, 41486L, 41487L, 41488L, 41489L, 
  36498L, 36504L, 36510L, 36515L, 36521L, 36524L, 36528L, 36530L, 
  36765L, 36769L, 36775L), class = "data.frame")
  </code></pre>